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The relationship between the geochemical characteristics of granite and the genesis of indium mineralization: a case study of the differences in granite mineralization in Gejiu, Yunnan Province

YAN Jinsheng), LIU Yingchao), MA Wang), ZHAO Sibo), YUE Longlong), JI Xuan), ZHENG Ning)

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Indium, a rare metal, plays an irreplaceable role in cutting-edge technology and is considered a critical mineral resource of the 21st century by many countries. Over the past decade, research on indium deposits has focused on deposit types, occurrence states, enrichment mechanisms, and mineralization processes, establishing a fundamental theoretical system for indium mineralization. However, comparative analysis of mineralization differences between different granite types and research on characteristic geochemical prospecting indicators for indium-bearing granite remain unexplored.This paper selects porphyritic granite from the Longchahe area in the western part of the Gejiu mining district in Yunnan as a representative of barren granite. Through zircon U-Pb dating and analysis of trace elements, whole-rock major and trace elements, Sr-Nd isotopes, and zircon Lu-Hf isotopes, a systematic comparative study with mineralization granite in the eastern part of the mining area is conducted to identify the controlling factors of differences in indium mineralization potential in granite.The results indicate that the rock-forming ages of barren rock bodies (85.26±0.4 Ma) and mineralization rock bodies (82.4±1.1 Ma~86.7±2.8 Ma) are similar, both characterized by silicon enrichment, slightly alkaline-rich, relatively potassium-rich, and pronounced Eu negative anomalies, indicating they are both S-type granite. Both granite types have low ε_Hf(t) values (-7.99~-5.73), high (₈₇^Sr/₈₆^Sr)_i values (0.71269~0.71309), low ε_Nd values (-7.4~-8.2), and a wide range of Nb/Ta ratios (10.1~16.8), suggesting they are products of homologous magma processes, derived from partial melting of the middle Proterozoic ancient upper crust with some mantle material involvement. The Ce₄₊^/Ce_³⁺ values (5.4~91.4) vary widely, Dy/Yb (0.24~0.49) values are relatively high, and zircon saturation temperatures (621.4℃~779.2℃) are low, indicating formation under low temperature, low oxygen fugacity, and water-poor conditions.Zr/Hf ratios and Rb/Sr ratios remain constant in typical magmatic systems, but when magma undergoes significant compositional changes due to differentiation, these ratios change significantly. The Zr/Hf ratios (16.48~63.15) of mineralization rock bodies are significantly lower than those of barren rock bodies (73.69~74.71), and the Rb/Sr ratios (1.87~27.44) of mineralization rock bodies are significantly higher than those of barren rock bodies (0.49~0.64), indicating different degrees of crystal differentiation. These characteristics suggest that differences in indium mineralization between different granite types are not related to the characteristics of the magma source area and the physicochemical conditions of formation, but are mainly controlled by the degree of magma crystal differentiation. Zr/Hf ratios, Rb/Sr ratios, and variations in rare earth element content can be used as indicators to determine the degree of magma differentiation and further infer whether granite is indium-bearing.
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Early Paleoproterozoic-late Neoarchean garnet granites from the Wulashan area, North China Craton: Genesis and geological significance

HUANG Daomao, KE Shan, LI Pengchuan, DONG Chunyan, LI Shuguang, WAN Yusheng

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Wulashan is located in the middle section of the Khondalite Belt, western North China Craton, with well-developed supracrustal rocks mainly composed of garnet-biotite gneiss. They underwent strong metamorphism, deformation and anateixs, resulting in the formation of garnet granite. This study conducted field geological, geochemical, and zircon SHRIMP U-Pb geochronological studies on the garnet granite. There are often transitional relationships between garnet-biotite gneiss, anatectic garnet-biotite gneiss and garnet granite, with the garnet granite exhibiting in situ to semi in situ properties. Four garnet granite samples have the metamorphic-anatectic zircon ages of 2442~2463 Ma. Considering the strong overprinting of late Paleoproterozoic tectonothermal event, it is reasonable to tentatively set the formation age of garnet granite between 2.45 and 2.5 Ga or closer to 2.5 Ga. This supports the conclusion that garnet-biotite gneiss formed in the late Neoarchean. The garnet granite shows large variations in elemental composition, with SiO2, TFeO, MgO, Na2O, and K2O contents of 66.41 %~73.79 %, 0.15 %~4.02 %, 0.07 %~1.57 %, 2.96 %~5.27 %, and 1.54 %~5.27 %, respectively. TREE, (La/Yb)n, and Eu/Eu* are 83.45×10-6~262.44×10-6, 11.2~182.6 and 1.15~3.62, respectively. They have whole rock εNd(t) of -0.18 to 1.65 and tDM2(Nd) of 2.60 to 2.77 Ga, while metamorphic-anatectic zircons have εHf(Hf) of -0.86 to 4.54 and tDM2(Hf) of 2.69~3.04 Ga. The significant variation of garnet granite in elemental composition largely reflect the differences in the composition of their source regions and the garnet differentiation degree during their formation process. The source rocks are late Neoarchean meta-clastic sedimentary rocks with different maturity (mainly garnet-biotite gneiss). The formation of the garnet granite marks a transition of the tectonic regime from compression to extension in the early Paleoproterozoic to the late Neoarchean, as well as the initial stabilization of the metamorphic basement.
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Petrography and sulfer isotopic compositions of the early Cambrian Ni-Mo polymetallic layer in the Yangtze Block：insights into sedimentary environment and mineralization

WANG Tianshun, FU Yong, YANG Zhen, WEI Shuaichao, YUAN Shunda, LUO Gan

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At the bottom of the Lower Cambrian Niutitang Formation along the southeastern margin of the Yangtze Block,a Ni-Mo polymetallic layer is deposited,enriched in elements such as As,Au,PGE,Re,Os,Cu,Zn,Cd,Ag,Sb,Se,Tl,and Hg. The genesis of these metal elements have long been debated. This study conducts detailed petrographic observations and in situ sulfur isotope analyses of the Ni-Mo polymetallic layer in the Gezhongwu section of Zhijin, Guizhou. Petrographic analysis reveals distinct mineralization stages for molybdenum and nickel：Molybdenum mineralization primarily occurred during the diagenetic stage of sedimentary rocks. Under mechanical compaction,fractures formed in collophane nodules,allowing molybdenum-bearing fluids to infiltrate the nodules along these fractures , where they combined with organic matter to form MoSC minerals. In contrast,Nickel sulfides are predominantly distributed at the edges of nodules or fill fractures in vein-like forms,indicating that nickel mineralization postdated molybdenum mineralization. Sulfur isotope composition analysis demonstrates that sulfides and sulfate minerals contemporaneous with MoSC mineralization exhibit lighter sulfur isotope compositions(-16.52‰ to -10.31‰),reflecting terrestrial input regulation of sulfate supply. Oxidative waters introduced by terrestrial input promoted the transformation of early framboidal pyrite into sulfate minerals. In contrast,sulfides and sulfate minerals coeval with nickel sulfides display heavier sulfur isotope compositions(+4.19‰ to +23.77‰),suggesting that as transgression intensified,the contribution of terrestrial sulfate diminished,resulting in sulfide sulfur isotopes approaching the δ₃₄^{S values of Cambrian seawater.} Combining petrographic observations with in situ sulfur isotope analyses,we propose that terrestrial inputs of phosphorus,organic matter,and sulfate served as critical material sources for the formation of the Ni-Mo polymetallic layer. Meanwhile, redox condition changes in seawater induced by marine transgression controlled the sequential differences in molybdenum and nickel mineralization.
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Genetic relationship between the Pb-Zn and Mo-Cu mineralization of the Jiawula deposit, Inner Mongolia, China: Constraints from in-situ major and trace elements and S isotope of pyrite

LIU Yanrong, WANG Yingfeng, SUN Guiyuan, ZHOU Yi, LI Chengze, TAN Huangbintao, AISHAN Mayila

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The Jiawula deposit is one of the representative Pb-Zn polymetallic deposits in the Erguna block. With Cu-Mo mineralization recently delineated in the deep porphyry, the researches on its ore-forming material source, and genetic relationship with the shallow Pb-Zn bodies are still lacking. In order to understand the enrichment mechanism and occurrence state of elements, scanning electronic microscope (SEM), electronic probe micro-analyser (EPMA) and laser ablation (multi-collector) inductively coupled plasma mass spectrometry (LA-(MC)-ICP-MS) are used to determine the microstructure, major and trace element concentrations, and sulfur isotopes of different types pyrites from the shallow Pb-Zn orebodies and deep Cu-Mo orebodies of the Jiawula Pb-Zn polymetallic deposit. Such understanding can provide insights into the genesis of the deposit. The hydrothermal mineralization process is subdivided into four mineralization stages: quartz-pyrite stage (I); quartz-sulfides polymetallic stage (II); quartz-sphalerite-galena-silver minerals polymetallic stage (III); and quartz-calcite-pyrite stage (IV). Pyrites are classified into four types (Py1~Py4) based on the mineralization stages. Our results show that Co, Ni and As are enriched in different types of pyrites through substitution. Py1 and Py4 pyrites are featured by high concentrations of Na, Al, K and Ti which possibly occur as oxide or silicate inclusions; Py1 and Py2 are weakly rich in Bi, and Py4 is rich in Cu, Pb, Zn, Sb and Ag which occur mostly as sulphide or sulphate inclusions in the pyrite; Py3 is commonly depleted in most trace elements. In situ sulfur isotope analysis of pyrites shows that Py1, Py2, Py3 and most of Py4 have similar δ34S values (0.68‰~4.83‰), indicating that the sulfur was derived from a deep magma. However, some of Py4 grains show obviously higher δ34S value (7.81‰~10.23‰), suggesting the sulfur was likely derived from the crust. On the basis of field observations, in situ microanalysis and previous studies, , the shallow Pb-Zn mineralization and deep Cu-Mo mineralization were formed in the same geological event and genetically linked to the magmatism that produced granitic porphyry and quartz monzonite porphyry. Therefore, we conclude that the Jiawula deposit belongs to the porphyry-epithermal polymetallic deposit type from the perspective of ore genesis.
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Research and significance of "anti watermelon" Elbaite from the Huanglongling lithium pegmatite deposit in Altyn ,Xinjiang

duxiaofei, wanghe, libin

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In recent years, the Huanglongling super-large pegmatite-type lithium deposit has been newly discovered in the Altyn of Xinjiang. The "anti-watermelon" Elbaite is developed therein. However, the "anti-watermelon" lithium tourmaline is rather rare. What are its coloring factors and what is its formation environment? And what is its indicative significance for the mineralization of rare metals such as lithium? In this paper, research was carried out through means such as TIMA , EMPA, in-situ trace element analysis, and boron isotope analysis. The analysis results show that the lithium abundance gradually increases from the core to the edge, while iron, manganese and zinc gradually decrease. The coloring elements of green Elbaite are mainly Fe and Zn, and those of pink Elbaite are mainly Mn. The "anti-watermelon" Elbaite in Huanglongling belongs to the normal magmatic evolution. The outer pink Elbaite has a higher degree of evolution and was formed later than the inner green Elbaite. The variation range of the δ11B value of the outer pink Elbaite is -15.31‰ to -14.63‰ (with an average of -15.04‰), and that of the inner green Elbaite is -14.94‰ to -14.55‰ (with an average of -14.75‰). The concentrated range of the δ11B values indicates that the boron isotope fractionation is not obvious, which may be related to the fluid exsolution in the melt-fluid stage. Meanwhile, the crystallization of lithium-containing minerals has a sequential nature. The appearance of lithium tourmaline indicates that the magma has a high degree of evolution, suggesting that the deep part of the Huanglongling area has the potential for super-large lithium-beryllium deposits.
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Geochemistry,geochronology,Carbon isotopes and genetic mechanism of the Jingshan graphite deposit in the Laiyang County of Shandong Province

LU Hao, JIANGGuohui, LIU Huan, MA Fang, WANG Haibo, JIANG Yuli, ZOU Jian, ZHANG Haifang

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The Jingshan region of Laiyang is situated in the western Jiaolai Basin, characterized by well-developed metamorphic rock sequences and serving as a significant producer of crystalline graphite. This study conducts geochemical, zircon U-Pb chronological, and carbon isotope analyses on the graphite deposits within the area, while also investigating their genetic mechanisms. The findings reveal that the graphite-bearing metamorphic rocks contain 60.31% to 73.63% SiO2, 10.99% to 16.59% Al2O3, 0.69% to 3.15% TFe2O3, 0.36% to 1.53% CaO, 1.03% to 5.31% K2O, and 1.31% to 6.16% Na2O. These rocks collectively display characteristics of being high in silicon and alkali, rich in aluminum, and poor in calcium, marking them as consistent with the Khondalite series.;The total amount of rare earth elements is low, ranging from 68.65×10-6to 183.66×10-6, with noticeable enrichment in light rare earth elements. They exhibit weak negative europium anomalies (average δEu is 0.92) and weak negative cerium anomalies (average δCe is 0.96), enriched in Rb, Th, Zr, Hf, Sm, and other elements, and depleted in Nb, Ta, Sr, P, and other elements; Carbon isotope analysis indicates that the δ13C of graphite in the ore ranges from -17.57‰ to -15.99‰, with the carbon primarily sourced from biogenic organic matter, suggesting a minor contribution from inorganic carbon. The 207Pb/206Pb age of the metamorphic zircon is 1823.80 ± 6.3 Ma, representing the late Paleoproterozoic era when the graphite-bearing biotite metamorphic rocks formed.Analysis of metamorphic protoliths, sedimentary structures, and provenance indicates that the protoliths of graphite-bearing metamorphic rocks in the Jingshan area are primarily sedimentary rocks, including greywacke, feldspar quartz sandstone, mudstone, and shale. They were formed in a shallow marine setting on the continental margin under conditions of weak to moderate reduction. The graphite deposits in this region represent carbonaceous sedimentary formations within Paleoproterozoic marine basins, which were subsequently metamorphosed through regional metamorphism and subsequent orogenic activities, resulting in
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Ore genesis of Fanjiabuzi talc deposit in Liaodong Peninsula: constrained by magnesium isotope evidence

LIU SiHan, Hu Guyue, ZHENG Jun, LIU KaiYuan, DONG JianJun, ZHAO Yue, WANG ChunLian

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The Fanjiabuzi talc deposit in the Liaodong Peninsula occurs within magnesite marble strata of Member three of the Dashiqiao Formation in the Paleoproterozoic Liaohe Group, representing a Mg-rich carbonate replacement-type talc deposit. This study conducted element geochemical and Mg isotope geochemical analyses on ore bodies and wall rocks of the Fanjiapuzi talc deposit. Results indicate that: (1) Talc ore bodies inherit the rare earth element (REE) and trace element geochemical characteristics of their marine sedimentary magnesite marble wall rocks; (2) Relative to the marine Mg isotope geochemical characteristics of Mg-rich marble strata in Member three of the Dashiqiao Formation (δ2?Mg: -1.03‰ to -1.12‰), the Mg isotope compositions of talc ores (δ2?Mg: -0.48‰ to +1.06‰) exhibit significant variations. Therefore, during the regional metamorphism of the Lüliang Orogeny affecting the Paleoproterozoic Liaohe Group Dashiqiao Formation, Mg-rich carbonate formations likely experienced multi-stage Si-rich metamorphic hydrothermal fluid replacement processes. These processes caused varying degrees of element partitioning and Mg isotope kinetic fractionation between carbonate and talc during the steatitization mineralization.
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Genesis of high Sr/Y granites in the Northern Langshan and its implications for the late Paleozoic tectonic evolution of the Alxa Block

ZHU Hongtao, GAO Qiang, LAI Lianxin, LI Xiaolong, LI Shuaibing, MIAO Tengfeng, LIU Xingguo, WEI Junhao

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Magmatic-tectonic events in the Alxa Block since the Early Paleozoic are believed to have been a response to the southward subduction of the Paleo-Asian Ocean. However, the timing of the closure of the Paleo-Asian Ocean in the Alxa Block remains highly debated. Early Permian adakitic porphyritic granites, widely exposed in the Tugurige area of northern Langshan, Alxa Block, may provide key insights into the tectonic setting of the Alxa Block and the closure timing of the Paleo-Asian Ocean. LA-ICP-MS zircon U-Pb dating indicates that the porphyritic granite formed at 286 Ma, coinciding with a magmatic hiatus during the Permian in the Alxa Block. Geochemical analysis reveals that the granite is aluminum-rich (Al2O3: 15.26% ~ 15.48%), alkaline-rich (Na2O+K2O: 7.95% ~ 8.25%), with low MgO (0.73% ~ 0.84%) and Mg# values (42.83 ~ 44.20). It is strongly depleted in heavy rare earth elements (low Y: 4.7×10?? ~ 5.7×10??; low Yb: 0.39×10?? ~ 0.46×10??), while exhibiting high Sr (628×10?? ~ 743×10??) and high Sr/Y ratios (123.14 ~ 143.40), which are characteristic of adakitic rocks. The εHf(t) values of magmatic zircons range from -0.37 to 4.01, and whole-rock Nd isotopes show slight depletion (εNd(t): -4.08 to -3.76). Combined with the Late Paleozoic Hf and Nd isotope evolution characteristics of magmatic rocks and crustal thickness changes in the Alxa Block, this study suggests that the Alxa Block was situated in a tectonic setting characterized by prolonged subduction and slab rollback of the Paleo-Asian Ocean during the Early to Middle Permian. The Early Permian adakitic intrusive rocks in Tugurige were likely formed in an extensional environment induced by slab rollback of the subducted Paleo-Asian Oceanic plate. This extensional environment triggered the upwelling of mantle-derived material, leading to the partial melting of the thickened lower crust and the formation of adakitic magma, which subsequently experienced limited mixing with coeval mantle-derived mafic magma during its ascent. These findings suggest that the Paleo-Asian Ocean in the Alxa Block had not yet closed prior to the Late Permian.
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Determination of the basalts from Chengjiang Formation in Huize area, western margin of Yangtze Block, and its indication to the disintegration of Rodinia supercontinent

WU Jialin, LIU JUNPING

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Through a detailed field investigation, two basalt interlayers were identified in the lower part of Chengjiang Formation in Huize area, the formation age and petrogenesis of these basalts has key implications for understanding the disintegration of Rodinia supercontinent. LA-ICP-MS zircon U-Pb geochronology , Lu-Hf isotopic and whole-rock geochemistry studies were perfomed on these basalts. The zircon U-Pb dating of the basalts yields an age of 802.3±5.2Ma(MSWD=0.43，n=18), indicating that the basalts formed in early Nanhau period. εHf (t) values of the basalts is between -4.2 ~ +5.7, the geochemistry characteristics show that the basalts are classified as a subalkaline tholeiite basaltic series, their Chondrite-normalized REE patterns and primitive mantle-normalized spidergrams are slightly inclined to right, similar to the characteristics of E-MORB, tectonic discrimination diagrams indicate that the basalts has geochemical feature of intraplate basaltic or MORB, the basalts are interpreted to have originated from partial melting of a spinel lherzolite lithosphere-asthenosphere interaction mantle source, and contaminated by the early mesoproterozoic crustal materials. This discovery indicate that the disintegration of Rodinia supercontinent has occurred before ~802Ma, oceanic crust was appeared in some ocean basins, and it is a important geochronology and petrology evidence of Kangdian rift broke up to a ocean, which further illustrates that it is more reasonable to palce the base of Jinnig movement at 802Ma.
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Research progress and prospect of the ophiolite peridotite in Turkey

CHEN Bohao), LIAN Dongyang), CAI Pengjie, BO Rongzhong)

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Turkey ophiolites are distributed across several tectonic units, such as the Northern Anatolian Belt, the Tauride Ophiolite Belt, and the Southern Ophiolite Belt. These ophiolites represent remnants of the Tethyan oceanic lithosphere and reflect the complex tectonic evolution of the region. Studies show that the mantle peridotites within these ophiolites, including harzburgite, dunite, and lherzolite, are extensively serpentinized and exhibit mineralogical and geochemical affinities with peridotites formed in abyssal and forearc settings. The mineralogical characteristics of mantle peridotites, such as the chemical compositions of olivine, orthopyroxene, clinopyroxene, and the Cr# and Mg# values of chromite, provide crucial insights into their melting history and tectonic origin. Geochemical analyses further reveal that mantle peridotites in Turkish ophiolites exhibit significant variations in rare earth element (REE) and trace element distributions, indicating varying degrees of partial melting and subsequent melt-rock interactions. Lherzolites display a left-leaning REE pattern with light REE depletion, while harzburgites and dunites show “U”- or “V”-shaped REE patterns resulting from interaction with LREE-enriched melts/fluids in suprasubduction zone settings. Chromitite research is a key focus within Turkey ophiolites, especially the distribution and genesis of podiform chromitites, which provide valuable guidance for chromitite exploration. Studies indicate that chromitite formation is influenced by a combination of mantle partial melting, melt-rock interaction, and magmatic fractional crystallization, with contributions from deep mantle materials. The mantle-crust transition zone and the upper part of the mantle in supra-subduction zone settings are identified as critical areas for chromitite formation. Moderately depleted peridotites, especially harzburgites associated with dunites, are important exploration indicators, while large-scale dunites of boninitic affinities provide favorable spatial conditions for chromitite enrichment. Additionally, the preservation and exposure of ore-bearing bodies, closely tied to the degree of erosion, are crucial factors to consider during exploration. In conclusion, the study of Turkish ophiolites not only deepens the understanding of mantle dynamics and plate tectonics but also provides scientific guidance for chromitite exploration. By integrating the petrological and geochemical characteristics of mantle peridotites, focusing on favorable tectonic settings, large-scale dunite regions, and moderately eroded ore-bearing bodies, future chromitite exploration efforts are expected to achieve greater efficiency and yield more significant results.
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Study on topographic amplification effect of strong earthquake ground shaking in the Yarlung Tsangpo Grand Canyon - A case study of the 2017 Miling Ms6.9 earthquake

Li Haowen, He Kai, Li Bin, Wan Jiawei, Gao Yao, Wang Wenpei, Cui Fangpeng

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The Ms6.9 magnitude earthquake occurred in the Yarlung Tsangpo Grand Canyon region of Minlin City, Tibet Autonomous Region, at 06:34 on November 18, 2017, which led to a number of large-scale landslide debris flows and river blockage in the uninhabited area of the Grand Canyon, resulting in serious hazards. In this paper, we use the 3D spectral element method SPECFEM3D numerical simulation program, combined with remote sensing image data, to simulate and study the ground vibration amplification effect of the complex terrain conditions of the Grand Canyon under the effect of the Ms6.9 magnitude earthquake in Minlin. The results show that: (1) when the seismic wave propagates along the Xixingla rupture, the velocity amplitude amplification occurs in front of the fault rupture, and the uneven energy of the seismic wave and the amplification of the velocity amplitude in many places occur when passing through the high and very high mountainous terrain of the Grand Canyon. (2) The simulated epicenter PGA of the Miling earthquake reached 4m/s2 (0.4g), and the high amplitude area was concentrated near the Xixingla rupture, which was mainly divided into the glacier aggregation area on the north side of the Gyala Peri Peak, the Jiala - Baimagouxiong section of the Yarlung Tsangpo River, the Xixingla - Naiqu section, and the Zhaqu - Duoka section. (3) The PGA of the Yarlung Tsangpo Grand Canyon in the area of rapid topographic change can be 1.97 m/s2, and the amplification rate can be up to 4 times from the bottom to the top of the mountain, and the maximum PGA of 4 m/s2 was detected above the concave and convex body of the seismic source model (4) Three major landslide-intensive zones appeared in the Yarlung Tsangpo Grand Canyon after the Milling earthquake, which were the Jiala-Baimagouxiong section, the Xixingla-Naiqu section, and the Zhaqu-Duoka section, and the PGA high amplitude area coincides with the distribution of landslide-intensive development area. The discussion can be concluded that the Milin earthquake has a non-negligible influence on the occurrence of high watershed-based geohazards in the Grand Canyon area after 2017.
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Rapid exhumation in Hainan Island and its implications for the formation of the South China Sea

Zhang Yulian, Zhang Wanfeng, Zheng Dewen, Li Chaopeng, Yu Jingxing, Li Pengfei

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The paleographic pattern of the southern margin of the South China Block before the Cenozoic is essential for understanding the formation and evolution of the South China Sea. Hainan Island, located at the northern margin of the South China Sea and adjacent to the southern edge of the South China Block, serves as a key region for investigating the paleographic features of the passive continental margin of the South China Sea. In this study, we conducted biotite 40Ar/39Ar geochronological analysis on granites from the Triassic to Cretaceous on Hainan Island, to explore the exhumation characteristics and topographic evolution during the Mesozoic. The results show that the cooling ages obtained from biotite 40Ar/39Ar range from 107 to 92 Ma The consistent cooling ages of granitic plutons along the periphery of Hainan Island suggest that the Hainan Island underwent rapid cooling during this period. By synthesizing the available biotite 40Ar/39Ar age data, we observe a “younger on the periphery, older in the center” cooling age distribution, indicating that during this period, the peripheral regions of Hainan Island experienced more significant exhumation than the central areas during this time. It is inferred that during the Late Mesozoic, Hainan Island exhibited a “high in the periphery, low in the center” topographic pattern. Based on this observation, we evaluate and select samples suitable for paleoelevation reconstruction, using detrital zircon Eu/Eu* anomalies and whole-rock (La/Yb)N and Sr/Y ratios. The results of paleoelevation reconstruction of the peripheral regions of Hainan Island during the Cretaceous indicate that the paleoelevation in this period exceeded 3000 meters. Rapid exhumation of the peripheral granitic plutons provided a substantial detrital material to the low-lying Baisha Basin in the central region, further supporting the “higher in the periphery, lower in the center” topographic feature. A comprehensive analysis of the geochronological, geochemical, and provenance data from the South China Sea peripheral blocks reveals that the region experienced a widespread exhumation/cooling event during the Early-Late Cretaceous. This suggests that, at least during the Late Mesozoic, the southern and northern margins of the South China Sea still existed as a unified entity, implying that the initiation of the South China Sea rifting occurred after this period.
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Geological characteristics and Zr-Nb-Th-REE metallogenic potential of Chahannuo alkaline pegmatites in the northern margin of Qaidam basin

Feng Xiaokun, Wang Zhiqiang, Yuan Feng, Deng Yufeng, Jing Delong, Li Xiaohui

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Alkaline rocks and related alkaline pegmatite are important sources of rare earth elements and rare metals (Zr, Nb, Th). The Qinghai-Tibet Plateau is an important treasure house of mineral resources in China, but alkaline pegmatite and related mineralization have not been reported. A number of Zr-Nb-Th-REE-rich pegmatites were found in the Chahanno area of the northern margin of Qaidam including zircon-titanite-pyroxene pegmatite, titanite-pyroxene pegmatite and allanite-titanite pegmatite. These pegmatites are typically characterised by coarse-grained pyroxene, titanite, zircon and allanite, and contain accessory minerals such as thorite, monazite, parisite-(Ce), fergusonite-(Y), and xenotime-(Y). Whole rock geochemistry shows that the Chahannuo pegmatites is mainly the alkaline-peralkaline series, and generally tend to be potassic. The petrographic and geochemical characteristics indicate that Chahannuo pegmatites belong to the miaskitic alkaline pegmatite, and the Nb-Y-F type in the Li-Cs-Ta and Nb-Y-F classifications. The weighted mean U-Pb ages of the zircon-titanite-pyroxene pegmatite and the titanite-pyroxene pegmatite are 436.3 ± 5.6 Ma and 435.2 ± 4.8 Ma, respectively, which are consistent with the continental collision in the northern Qaidam margin and the mineralization related to alkaline rock in the Qilian-Qinling-Kunlun tectonic belt during the late Caledonian. The high contents of Zr, Nb, Th and REE elements in the Chahannuo pegmatites indicates that there is a significant metallogenic potential and prospecting prospect of Zr-Nb-Th-REE in the Chahannuo area.
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Iron isotope compositions evolution of the early Ediacaran cap carbonate on the Yangtze Block

Yan Bin, Zhu Xiangkun, Li Jin, Ma Jianxioang

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Iron is pivotal in the global biogeochemical cycles and holds considerable significance for comprehending the surface environment and biological evolution during the early Ediacaran Period. This research concentrates on the cap carbonate of the Ediacaran Doushantuo Formation located in the Jiulongwan section of the Xiajiang region, southern China. Utilizing dilute acetic acid leaching to extract iron isotopic compositions from carbonate phases, the study reconstructs the iron isotopic evolution curve of early Doushantuo seawater, which exhibits a three-stage variation characterized by a decrease, an increase, and a significant decrease. During the deposition of the cap carbonate, the iron cycle was initially dominated by iron input from glacial meltwater, succeeded by the control of pyrite burial in the intermediate stage, and ultimately, the extensive burial of iron oxides in the late stage. The oxidation of water bodies in the later stage of cap carbonate deposition established a suitable ecological environment for the survival and development of microorganisms, thereby promoting biological evolution and radiation during the early Ediacaran Period. The dynamic changes in marine iron cycling during the early Ediacaran offer new insights into the interplay between environmental and biological evolution during this critical juncture in Earth''s history.
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Research on Ar~Ar dating method for oceanic polymetallic nodules: a case study of the CC region in the Pacific Ocean

WANG Naichuan), CHEN Wen), REN Jiangbo), HE Yulin)

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The dating methods for polymetallic nodules currently mainly include Be dating, K~Ar dating, U-series isotope dating, Re~Os dating, and Sr isotope dating, but each method has certain limitations. For example, the age range value measured by Be method and U dating method is small, only 0-1.5 Ma; The K~Ar method not only requires a large sample size, but also K and Ar element are not measured on the same sample, which can cause significant errors due to sample heterogeneity; The rhenium osmium method and Sr isotope method are used for dating polymetallic nodules, but due to issues with the test objects, the testing accuracy is relatively low. This study adopts the Ar~Ar dating method, which not only has a wide dating range and requires a small sample size, but also measures the content of K and Ar on the same sample. Only the isotopic ratio of Ar needs to be measured, and there is no need to measure the absolute content of K and Ar separately, so there is no need to worry about the heterogeneity of the sample. Therefore, the Ar~Ar dating method has high accuracy. This study used a step-by-step layering technique to select Vernadite; Adopting the method of reducing neutron flux, decreasing irradiation time, and increasing irradiation isolation for fast neutron irradiation; An Ar~Ar dating experimental procedure was established for oceanic polymetallic nodules, and the ages of the core and crust of polymetallic nodules in the CC area of the eastern Pacific were analyzed to be 32.0~42.2Ma and 38.6~44.3Ma. The growth rate of the crust was calculated to be 0.6~1.2mm/Ma.
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Genesis of the Sartohay Podiform Chromitite Based on Microinclusions in Chromite

WenXingying, ZhuYongfeng

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Here, we present a petrographic and microanalytical study of microinclusions in chromite from podiform chromitites hosted by the Sartohay ophiolitic mélange in west Junggar, northwestern China, to investigate the parental magma evolution and chromitite genesis. These silicate inclusions comprise olivine, enstatite, diopside, amphibole, and Na-phlogopite. Their morphological characteristics suggest that most inclusions crystallized directly from the captured melt, with a few anhydrous inclusions (olivines and pyroxenes) as solid silicates trapped during the chromite crystallization. Equilibrium pressure–temperature conditions of coexisting enstatite–diopside inclusions are 8.0~21.6 kbar, and 874~1048 °C. The high Na2O and TiO2 contents of hydrous minerals indicate that the parental magma of chromitites was hydrous and enriched in Mg, Na, Ca, and Ti. The calculated Al2O3 content and FeO/MgO ratio of the parental melts in equilibrium with chromite showed MORB affinity. However, the TiO2 values of parental melts and TiO2 contents of chromite evoked parental MORB-like tholeiitic melts. The composition of olivine inclusion was determined, and it was revealed that the primary melts of the Sartohay podiform chromitites had MgO contents of ~22.7 %. This aligns with the observed high magnesian signature in mineral inclusions (Fo = 96~98 in olivine, Mg# = 0.91~0.97 in diopside, and Mg# = 0.92~0.97 in enstatite). We propose that Sartohay podiform chromitites initially formed through the mixing/mingling of primary hydrous Mg-rich melt and the evolved MORB-like melt derived from the melt–peridotite reaction in the upper mantle. In this process, the continuous crystallization of chromite captured micro-silicate mineral inclusions, finally leading to the formation of the Sartohay podiform chromitites.
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Restriction of Kaolinite on lithium isotope fractionation and rare earth element enrichment and mineralization during weathering of rare-earth rich granite: A Case Study from Zudong，Southern Jiangxi Province

LIU Wenbin, Tian Shihong, He Chuan, Yu Yushuai, Hu Wenjie, Chen Lu, Gong Yingli, Wang Yun, Li Haili, Sun Jiandong

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Lithium (Li) isotopes have emerged as a novel isotopic indicator for elucidating continental weathering processes in recent years. As one of the important continental crust rocks,the fractionation behavior of Li isotope in the weathering process of granite has attracted much attention. Moreover,the weathering crust of rare-earth element (REE)-rich granites serves as a crucial medium for the formation of ion-adsorbed REE deposits. Nevertheless,the fractionation behavior of Li isotopes during the weathering of REE-rich granites and its correlation with REE enrichment remain poorly understood. In this paper,the weathering profile of a typical rare-earth rich granite in Zudong area of southern Jiangxi Province was taken as the research object. Samples of weathering bedrock and its different weathering strata were systematically collected,and their contents of major and trace elements and δ7^{Li values were respectively determined.} Their mineral characteristics and contents were quantitatively analyzed by the automatic Comprehensive Mineral Analysis System (TIMA). The results show that the mineral composition of the bedrock and weathering samples mainly consists of Quartz,Orthoclase,and Albite. Clay minerals include Kaolinite,with a small amount of Chlorite and Illite. The bedrock belongs to altered granite (CIA=62.7), and altered secondary clay minerals can be seen during the initial weathering process. The concentration of REE in the weathering profile ranges from 54.2×10-6^~606×10-6^{, with the ratio of light REE to heavy}(LREE/HREE) varying 0.11~0.32, and the normalized ratio of lanthanum to ytterbium (La/Yb)N ranging from 0.10~0.32. REE exhibit a pronounced enrichment in the upper portion of the total regolith, falling within the scope of disclosure distribution. The distinction between light and heavy REE is significant. The δ7^{Li values in the upper part of the}total regolith range from -3.00%~-3.34%,and the δ7^{Li values in the lower part of the}total regolith range from -3.14%~-1.86%,both lower than the δ7^{Li value of the}bedrock (-1.70%). Based on the petrographic and geochemical data of the weathering profile,the fractionation of lithium isotopes in weathering profiles is predominantly controlled by the preferential adsorption of 6Li onto kaolinite, whereas the release of 7Li from primary minerals exerts a relatively minor influence on Li isotopic fractionation. The enrichment and fractionation of REE in the weathering profile are mainly influenced by secondary minerals,including the different adsorption of light and heavy REE by Kaolinite and the formation of rare earth-containing secondary minerals. Both Li isotope fractionation and rare earth element enrichment are constrained by Kaolinite,but the fractionation of Li isotope has no obvious relationship with the enrichment and differentiation of REE,and Li isotope cannot be regarded as a sole indicator for rare earth mineralization.
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Metallogenic potential discrimination of Baihuacao granite in Kafang Gejiu, Yunnan : Zircon geochronology, geochemistry and Sr-Nd-Hf isotope evidence

Yu Bo, Kong Zhigang, Mou Minghai, Wang Yu, Xu Fajin, Fan Zhuguo, Chai Wei, An Peng

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Granite bulge has always been an important prospecting indicator in Gejiu area,Kafang copper-tin polymetallic deposit is closely related to Xinshan granite body. However,the Xinshan rock mass is deeply inserted underground near the Xianrendong fault. The prospecting direction is unknown because the granite bulge is not detected to the south of the Xianrendong fault. In recent years, the deep prospecting project has exposed the Baihuacao granite body on the south side of the Xianrendong fault. The chronology and geochemical characteristics of the Baihuacao rock mass are the key to solving the prospecting bottleneck in this area. In this paper, the Baihuacao rock mass is taken as the research object. Through the study of petrography, zircon U-Pb chronology, Hf isotope, whole rock geochemistry and Sr-Nd isotope, the geochemical characteristics of Baihuacao rock mass, ore-forming rock mass and lean ore rock mass in this area are compared and analyzed, which provides a basis for prospecting prediction in this area. The zircon U-Pb age of the rock mass is 83.12±0.54 Ma, the SiO2 content is 74.504%~76.812%, and the K2O/Na2O ratio is between 1.35~1.64, which is a high-silicon, alkali-rich, high-potassium calc-alkaline series rock mass, 1< A/CNKA<1.1, showing quasi-aluminous to weakly peraluminous characteristics. It is enriched in large ion lithophile elements such as Rb, Th, U and K, and depleted in high field strength elements such as Ba, Nb, Sr, P, Zr and Ti. The total amount of rare earth elements ( ∑REE) is between 132.00×10-6~238.64×10-6. The differentiation of LREE and HREE is not obvious, with strong negative Eu anomaly (δEu is 0.03~0.09), which is Similar to the Xinshan rock mass, in contrast, the two are obviously different from the non-mineralized Longchahe rock mass in the western region.. The whole rock (87Sr/86Sr)i is 0.726236~0.7789159, εNd (t) is ?9~?8.1, and the corresponding two-stage model age tDM2 (Nd) is 1.54Ga~1.62Ga. The εHf (t) is ?9.15~?4.9, and tDM2 (Hf) is 1.46Ga~1.72Ga, indicating that the rock mass is formed by high degree of separation and crystallization of the parent magma formed by partial melting of the Mesoproterozoic strata under the background of lithospheric extension in western South China, which is similar to the Xinshan rock mass, indicating that the Baihuacao rock mass and the ore-forming rock mass in Gejiu area are derived from the same magma chamber. The rock mass is highly consistent with the Xinshan rock mass in the degree of provenance and differentiation evolution, and is obviously different from the Longchahe ore-poor rock mass in the region. The difference in provenance and magmatic properties and evolution degree is the main reason for the difference in metallogenic potential of different rock masses, indicating that there is an important prospecting potential between the Xianrendong fault and the Longshujiao fault.
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Fe-Cu-S isotope characteristics of the Dabaoshan copper deposit, Guangdong Province, and their implications for ore genesis and mineral exploration

Zhao Chenhui, Wang Denghong, Wang Chenghui, Qin Yan, Zhao Ruyi, Liu Wusheng, Zhang Xiong, Jiang Jinchang, Li Tingjie

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Despite over 65 years of development and research, the ore-forming processes and material sources of the Dabaoshan copper deposit in Guangdong remain debated. Fe and Cu isotopes are effective tools for constraining ore-forming processes and tracing the sources of ore-forming materials. However, Fe and Cu isotope studies have not yet been conducted at Dabaoshan. This study delineates the ore-forming processes and material sources of the Dabaoshan copper deposit through analysis of Fe, Cu, and S isotopes. The δ??Fe and δ??Cu values in the Dabaoshan copper deposit vary from -0.49‰ to 0.82‰ and -1.29‰ to 0.69‰, respectively. The lower δ??Fe values of chlorite-epidote-actinolite skarns and skarn-type copper ores indicate that the ore-forming fluids responsible for skarn were enriched in light Fe isotopes relative to the surrounding rocks. Chalcopyrite from the Dabaoshan copper deposit has δ??Cu values ranging from -1.29‰ to 0.51‰, with a variation of 1.8‰, suggesting significant Cu isotope fractionation during high-temperature mineralization. The negative correlation between copper grade and δ??Cu values in chalcopyrite, along with spatial zoning features, shows that copper mineralization is better along B3 and B5 lines compared to B0 and B9 lines. Correspondingly, chalcopyrite in B3 and B5 lines is enriched in light Cu isotopes. This spatial zoning pattern, combined with the minimum δ??Cu values in chalcopyrite, indicates that the deeper parts of the B3 and B5 lines still hold exploration potential. The Fe-Cu-S isotope compositions of the Dabaoshan copper deposit are similar to those of globally typical porphyry-skarn copper deposits. Particularly, the δ3?S values from 548 samples (from this study and previous research) dominatedly vary between -2‰ and 2‰, reflecting characteristics of magmatic sources, and are significantly different from those of volcanogenic massive sulfide deposits. The Fe and Cu isotope results, combined with the previous geochronological analysis of Dabaoshan, suggest that the dacite porphyry may not be the causative rock of the Dabaoshan copper deposit.
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Petrogenesis and geological significance of late Neoarchean high-Mg basalt-andesites in Western Shandong Province

YU Yang, LI Dapeng, CHEN Yuelong, LI Sanzhong, SUN Guozheng, ZHANG Chao

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The late Neoarchean mantle-derived magmatism in the Western Shandong of eastern North China Craton is complicated and diverse, which is the key to understand the dynamic mechanism of early crustal formation and evolution. In this study, field investigation, petrology, whole-rock geochemistry, and zircon U-Pb isotopes are reported for the late Neoarchean metabasalt-andesites from the Western Shandong. These late Neoarchean (2.55 Ga~2.53 Ga) metabasalt-andesites are characterized by high MgO (> 8%), low TiO2 (< 0.61%) contents with enriched light rare earth elements and large ion lithosphere elements, belonging to high-Mg basalt-andesite. Petrogenesis studies reveal that these high-Mg basalt-andesites were derived from depleted mantle source that metasomatized by subduction processes. The high-Mg basalt-andesites, together with the late Neoarchean sanukitoids, calc-alkaline basalts in the Western Shandong documented subduction processes, implying the modern-style plate tectonics including slab rollback may have operated during the late Archean.
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Geological characteristics, geochronology and zircon Hf-O isotopes of migmatite in Baicheng County, South Tianshan, Xinjiang

Lihaizhou, Huanghe, Wuhuanhuan, Panbeibei, Yaoxuejiao, Xuehuaimin

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Migmatization, recording the crustal anatexis, plays a vital role in continental crustal evolution; it can occur at various stages of orogenesis and is considered direct petrological evidence for crustal growth and reworking. The South Tianshan Orogenic Belt (STOB) is in the southwestern segment of the giant Central Asian Orogenic Belt. The formation of STOB was associated with long-term subduction of the South Tianshan Ocean and subsequent continental collision. In Laohutai Uplift, Baicheng County, some outcrops of migmatites have been found in Muzha’erte Formation that belongs to the Precambrian basement of northern Tarim Craton. This study conducted systemical geochronological, whole-rock geochemical, and zircon Hf-O isotopic studies. The results show that the studied migmatites were formed by partial melting of supracrustal rocks dominated by volcanic components. Based on geochemical characteristics, the migmatite samples were categorized into two groups. Samples predominantly composed of leucosomes consistently exhibited negative anomalies in Nb, Ta, and Sr, with insignificant Eu anomalies. In contrast, samples primarily consisting of melanosomes demonstrate not only negative Nb and Ta anomalies but also pronounced positive Sr and Eu anomalies. All samples present a relatively gentle right-inclined curve rare earth element pattern characterized by enrichment in light rare earth elements (LREE) and depletion in heavy rare earth elements (HREE). Zircons were classified based on their morphology and genesis. The U-Pb age peaks of zircons with anatectic characteristics in both leucosomes and melanosomes range predominantly from 436 Ma to 376 Ma. This age distribution suggests regional anatectic events occurring mainly during the Middle Silurian to Late Devonian periods. The εHf(t) values for the anatectic zircons from the melanosomes range from -15.98±0.96 to -2.06±0.89, with a TDM2 from 3.0 to 1.6 Ga, and δ18O values vary between 4.14±0.20‰ and 9.93±0.27‰. For the anatectic zircons from the leucosomes, their εHf(t) values range from -15.7±1.5 to -1.69±0.6, with a TDM2 from 2.4 to 1.6 Ga, and δ18O values vary between 4.30±0.23‰ and 10.02±0.2‰. In combination with previous studies, this study establishes the genetic link between the southward subduction of the South Tianshan Ocean and the anatectic events. A regional tectonic transition took place around ca. 420 Ma. The low-angle, advancing subduction during ~460~420 Ma resulted in an overall compressional background in STOB and the northern Tarim margin. In such a compressional setting, the supracrustal rocks were underthrusted into the deep depth of the crust, with limited anatexis. Subsequent to the tectonic transition, retreating subduction (or slab rollback), dominated the ~420 to ~390 Ma subduction; accompanied by extensive mantle underplating and a significant increase in geothermal gradient, the upper plate was in an extensional framework during this period. Intense anatexis took place in the context of such tectonic transition.
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Lithological characteristics of the mantle source for the Cenozoic potassic volcanics in Wudalianchi, Northeast China ——Constrained by the composition of olivine phenocrysts

Zhao Yu Xiao, Ge Zi Yi, Zeng Gang, Li Yu, Liu Jian Qiang, Chen Li Hui, Yu Hao Yuan, Zhou Zhong Biao

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Basalt is produced by partial melting of the mantle, and the early-crystallized olivine within it can reveal the composition and lithology of its mantle source. Previous studies have suggested that recycled materials, such as sediment and oceanic crust, are present in the source of potassic volcanics from Northeast China. Therefore, the source lithology of potassic volcanics can be identified through the compositions of the olivine phenocrysts that crystallize from them, which can also provide important insights into the deep cycling of those surface materials. Here, systematic sampling was conducted in the Wudalianchi region, a typical area of potassic volcanics, and olivine phenocrysts from 12 volcanoes (e.g., Xiaogushan, Molabushan, and so on) were selected for analysis. We found that these olivines show significantly compositional heterogeneity. Some olivines exhibit low Mn/Fe ratios and moderate Ni/(Mg/Fe) ratios, consistent with previous studies, which resemble those olivines crystallized from eclogite-derived melts. Other olivines show high Ni contents and high Fe/Mn ratios, consistent with those olivines crystallized from melts derived from reactive pyroxenites. This finding again confirms the diverse lithology of the mantle source of potassic volcanics from Northeast China. Further modeling suggests that the presence of eclogite (high-silica) is the key to explaining the high FeO/MnO ratios observed in the Wudalianchi potassic volcanics. During their ascent, the melts formed by partial melting of this recycled component undergo melt-peridotite interaction, and the composition of the finally crystallized olivines can account for the variation in Fe/Mn ratios observed in the olivine phenocrysts of the Wudalianchi volcanics.
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Ore-controlling structure，mineralogenetic epoch，and exploration directions of the Herenping gold deposit in western Hunan，South China

LIBIN, baidaoyuan, xuderu, Liuwanshen, hehongsheng, shaoyongjun, chenjianfeng, zengguangqian, chenxu, wenchunhua, dengxin

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The Herenping gold deposit is located in the middle section of the Xuefeng tectonic belt and is the largest gold deposit in the Liulincha gold ore-field. Previous studies have focused on the geological characteristics, ore-forming fluids, and material sources of the deposit; however, they have not clarified the key scientific problems concerning the ore-controlling structures and mineralogenetic epoch. These unresolved issues constrain our understanding of the genesis and exploration potential of the deposit. In this study，a large number of structural observations and analyses were carried out on surface outcrops and underground tunnels in these areas, and hydrothermal apatite that is closely related to mineralization was dated by LA-ICP-MS U-Pb dating. In combined with the regional tectonic evolution framework，we clarified the deformation sequence and tectonic setting of the study area，as well as the "transport-distribute-bear" ore-controlling structural system of the deposit. The mineralogenetic epoch was determined，and the ore genesis，ore-controlling structures，and favorable exploration directions were discussed. The main achievements and understandings are as follows: (1) The Herenping area experienced six major deformation events (D1 to D6): D1 corresponds to NW compression during the mid-Neoproterozoic Wuling movement, D2 to NNW～S-N compression during the Late Silurian Caledonian movement, D3 to NW compression during the early Indosinian movement in the mid-Triassic, D4 to NWW～E-W compression during the mid-Jurassic early-Yanshanian movement, D5 to NW-SE extension from the late Jurassic to Cretaceous, and D6 to NE compression during the middle to late Paleogene. Mineralization occurred during the D5 extensional period. (2) The ore-transporting structures in the Herenping gold deposit are deeply concealed NE-trending faults formed during D3 and D4. Ore-distributing and ore-bearing compatible structures are shallow NE-trending faults also formed during D3 and D4. The primary ore-bearing structures consist of NEE-trending folds, interlayer fractures formed during D2, and NE-trending faults formed during D3. A connecting 'bridge' structure controls the occurrence of thick and large orebodies. (3) LA-ICP-MS U-Pb dating of hydrothermal apatite yielded an age of 126.6±10.1 Ma (1σ, n=47, MSWD=1.4), indicating, combined with the formation tectonic setting of the ore-controlling structures, that the Herenping gold deposit formed in the Early Cretaceous. The mineralization relates to large-scale lithospheric extension and deep-seated magmatic activity caused by the westward subduction, roll-back, detachment, and sinking of the paleo-Pacific plate during the Yanshanian. Early structural reactivation was crucial for mineralization. (4) The next step in exploring the Herenping gold deposit should focus on the shallow NE-trending ore-transporting structures and extend to deeper levels. Regional prospecting needs to concentrate on basement uplift areas, especially those with NE-trending fault structures and NEE-trending structure compounds.
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Structural classification ore-controlling regularities and tectonic combination styles for hydrothermal superposition period of the Dahongshan cobalt-bearing copper-iron deposit in central Yunnan

ZHOU Yinkang, HAN Runsheng, ZHAO Dong, GONG Hongsheng, MENG Liuqing, QIU Wenlong, KANG Xuhao, MAO Xing

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The Dahongshan copper-iron deposit, located in central Yunnan, is a quintessential example of copper and iron metallogenesis within the Kangdian copper-iron polymetallic metallogenic belt. This deposit is distinguished by its diverse co-associated elements, complex metallogenic processes, multi-phase tectonic composites, and multiple mineralization styles. The ore bodies are hosted within the shallow metamorphic volcanic-sedimentary rock system of the Paleoproterozoic boundary, with the accumulated reserves of iron and copper metals classified as super-large deposits. From shallow to deep incised fracture zones, the deposit exhibits widespread hydrothermal superposition-type copper-iron ore bodies (veins). However, the spatial distribution characteristics of these vein-like ore bodies and their tectonic control mechanisms remain poorly understood, and the ore-controlling tectonic system and its controlling process are not known. Based on the large-scale tectonic-alteration petrographic mapping at various scales and depths, coupled with detailed analysis of the tectonic geometry, kinematics, and mechanical properties of the hydrothermal vein ore bodies, this study elucidates the metallogenic tectonic system during the hydrothermal superposition period. The findings reveal that the metallogenic tectonic system during the hydrothermal superposition metallogenic period is the NE tectonic zone of the Chengjiang period, under the action of the NW-SE oriented main compressive stress, governs the distribution of ore deposit, ore bodies and veins. This tectonic framework forms a hierarchical control system, with different scales of tectonic assemblages influencing ore distribution. Specifically, the spatial distribution of the deposit is controlled by the Dibadu dorsal fold and its associated fracture and jointing rift systems. At the ore body (vein) scale, the distribution is regulated by 'multi-character' and 'in-character' tectonic assemblages. This research provides critical insights into the hydrothermal superposition mineralization processes and offers valuable guidance for ore exploration within the Kangdian copper-iron metallogenic belt.
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Paleoclimate change and its driving mechanisms in the Gonghe Basin (NE Tibetan Plateau) in the Middle to Late Miocene

Luan Tianxinag, Zhang Bo, Zhang Jinjiang

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The paleoclimate of the northeastern Tibetan Plateau during the Middle to Late Miocene may have been controlled by tectonic uplift in the northeastern plateau and global cooling. To investigate the impact of global climate change and tectonic activity on regional climate, as well as to enhance understanding of the interactions among Earth's spheres, this study focuses on the Miocene sediments from the Gonghe Basin in the northeastern Tibetan Plateau. By integrating existing stratigraphic paleomagnetic age data with comprehensive analyses of branched glycerol dialkyl glycerol tetraethers (brGDGTs), total organic carbon isotopes, total organic carbon content (TOC) and heavy mineral composition, we reconstructed the environmental evolution history of the Gonghe Basin during this period. The results show that from 14.5 to 8.7 Ma, the paleotemperature reconstructed by brGDGTs steadily decreased (by about 2.3 ℃), the total organic carbon isotopes increased from -25.23‰ to -24.88‰, pH value increased from 8.1 to 8.7, and TOC decreased by ~0.05%, indicating an intensification of aridification. From 8.7 to 6.8 Ma, the total organic carbon isotope decreased from -24.88‰ to -25.23‰, and the pH decreased from 8.7 to 8.2, indicating that the aridification was alleviated. Compared with the previous period, the cooling rate accelerated (increased from 0.4 ℃/Ma to 1.7 ℃/Ma), and the content of unstable heavy minerals increased. It is inferred that during this period, the significant uplift of the Elashan and Qinghai Nan Shan around the Gonghe Basin formed a topographic barrier to the southeast monsoon, leading to opposite trends in temperature and humidity within the basin. By integrating the tectonic and climatic records from the northern Tibetan Plateau, we believe that the alleviation of aridification in the study area and regions to its east during 9~7 Ma primarily responded to the orographic rainfall effect caused by tectonic uplift. In contrast, the continued aridification since the Middle Miocene in areas to the west of the study area, such as the Qaidam Basin and Tarim Basin, was controlled by both global cooling and tectonic uplift.
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Tectono-thermal evolution of the basin-range system in the north margin of Erlian Basin and its geological significance

ZhouGuiLin, LI Ke, TANG Jianzhou, ZHANG Zhicheng, ZHANG Huaihui, DING Cong

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The Erlian Basin is a group of fault basins formed under the Mesozoic extension system in central Inner Mongolia. It is of great significance to study the characteristics of tectono-thermal history of the basins and identify the evolution law of tectono-geomorphologic exhumation in Inner Mongolia and its adjacent areas for understanding the dynamic mechanism of multi-tectonic domain superimposed transformation in NE China during the Mesozoic. Here, the apatite fission track (AFT) method is used to study the tectono-thermal evolution of the Bayindulan Sag and the Bayinbaolige Uplift in the northern margin of Erlian Basin. AFT dating results showed that the AFT ages in the Sag are 65.6±8.8~245.2±17.3 Ma, and the mean track lengths are 12.17±0.3~13.32±0.2μm. The ages of AFT in the Uplift region are 182±11~238.8±8.7 Ma, and the mean track length was 12.86±0.30~13.46±0.16 μm. The results of thermal history modeling show that the northern margin of Erlian Basin mainly experienced three stages of cooling, namely, late Paleozoic to Middle Jurassic (270-160 Ma), Late Jurassic to Early Cretaceous (160-100 Ma) and Late Cretaceous (100-70 Ma). Combined with the regional data, the tectono-thermal process in central Inner Mongolia presents three stages of evolution, and the late Paleozoic-Triassic uplift is related to the closure of the Paleo-Asian Ocean；During the Jurassic and Early Cretaceous, the central region of Inner Mongolia was affected by the extension collapse after the closure of the Mongol-Okhotsk Ocean and the subduction of the Paleo-Pacific plate. In the Late Cretaceous, the collision of East Asian continental margin blocks caused regional tectonic inversion in Erlian Basin. After the Late Cretaceous, the central part of Inner Mongolia did not experience significant cooling exhumation and the planation surface of Inner Mongolia Plateau was basically formed.
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Geochronology and geochemistry of deep-time volcanic ash and its geological implications from the Lakharpata Group in Nepal Lesser? Himalaya

LI Zaihui, WEI Hongwei①, YANG Ping, HE Lei, SHI Meifeng, WANG Zhenghe, DU Baiwei

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Time bracketing of thousands-of-meters-thick, low-grade metamorphosed, fossil-free sedimentary sequence of Lesser Himalayan is a longstanding challenge in Indian Proterozoic stratigraphy. Especially the uncertainty of the absolute age of the Lakharpata group not only hinders the comparison between the Himalayan region and the Indian Craton, but also cause diversity in the configuration? of Columbia supercontinent. The discovery of deep-time tuffs in the Lakharpata group provides the possibility to solve this puzzle. Bentonite layers were discovered in black organic shale at the base of the Lakharpata Group in Surkhet area. Bentonites are mainly composed of clay minerals, sericite, a small amount of quartz, and accessory minerals such as zircon and apatite. Zircons from bentonite exhibit typical internal structure and trace element composition characteristics of magmatic zircon. Geochemical? compositions of samples identify them as rhyolite with high potassium series(Al2O3=22.81～24.30%,K2O=8.23%～8.61%,SiO2=54.82%～55.82%). Rare earth element distribution is typical of granitic rocks,with a negative Eu anomaly of 0.54-0.59. The samples are depleted in Sr, Ba, Nb, and Ti elements, while Pb and Hf exhibit positive anomalies. The LA-ICPMS U- Pb age of zircon is 1652 ± 45 Ma, which limits the age of the bottom of the Lakharpata group. Combining with lithological assemblages, paleontological features, geochronology and volcanic stratigraphy, the Lakharpata Group can be compared with the Semri Group of the Vindhyan Supergroup in the Indian Craton, and meanwhile ,highly consistent with the Chang Cheng Group in the North China Craton in these aspects. The parent magma of Bentonites mainly composed of granite, accompanied by a small amount of basic rocks. The thickness of tuffs and grain size of zircon? reveal that the volcanic ashes were sourced from a volcanic event likely with a volcanic eruption index (VEI)? of 8, and transported 1000 km away . The analysis of Chemical Index of Alteration (CIA) value characteristics and trace element ratios indicate that the paleoclimate at that time was warm and humid. Through various methods of discrimination and combined with regional tectonic background, it is believed that volcanic activity was formed in an intraplate rift environment. Sedimentary assembly and thickness of? Lakharpata Group is considered , it indicate that ,from this time on , the North India Craton
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Evolution of ore-forming fluids in the deep polymetallic mineralization in western Xiangshan uranium ore field, Jiangxi Province, China: evidences from altered wall rocks

LiuJungang, LI ZiYing, ZHANG WanLiang, NIE JiangTao

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The Xiangshan uranium ore field, the largest hydrothermal uranium ore field in China, is hosted in early cretaceous felsic volcanic rocks. In recent years, , a discovery of hidden lead-zinc-silver mineralization in deep reach was achieved through NO.3 sientific deep drilling(CUSD3) in western Xiangshan uranium ore field. In this paper, the petrography and geochemistry of altered wall rock at different stages of polymetallic mineralization are studied. The rescults show that, sericitization-muscovitization and chloritization are the mayor alteration types, followed by silicide and carbonatization in quartz-arsenopyrite-chalcopyrite stage(S1 stage),. While in the no-mineralization pyrite stage (S2 stage), pyritization become dominant, followed by sericitization, chloritization, silicide and carbonatization. In Lead-zinc polymetallic mineralization stage (S3 stage), the main alteration types are sericitization and chloritization, followed by carbonation, silicification, pyritization, and in the lead-zinc-silver carbonate stage(S4 stage), carbonatization become strong, followed by sericitization, chloritization and silicide. Geochemical study of the alteration rocks shows that intense pyritization is the main factor which caused Fe increase in altered wall rocks, which indicates that the ore-forming fluid is rich in Fe2+^{and S}2^-, and the mobility of Na, K and Ca in altered rocks is mainly due to the sericitization of K-feldspar, plagioclase and biotite, and the migration of Rb, Ba and Eu in altered rocks is related to sericitization, while Nb, Ta, Zr and Hf have no migration, mainly related to the stability of titanite and zircon. In conclusion, ore-forming fluid is magmatic original hydrothermal fluid, which is rich in alkali metal elements (Li, Cs、K), sulfur ore-forming elements Cu, Pb, zinc, Sb, Mo and Volatile ions (H+^,CO2, HS-^{, Cl}^-). In additon, the increase of pH, and the gradual decrease of K+^{and H}+^{, may be the main factors of precipitation of metallogenic elements such as zinc and lead.}
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Characteristics and Geochronology of Ductile Deformation in the Bayan Obo Ore District and Their Geological Significance

WANG Dongsheng, GAO Yupu, SHE Hongquan, ZHANG Li, LI Yike, GUO Bin, KE Changhui, YUAN Xingyu, MA Shouxian, ZHU Zeying, PENG Zidong

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The Bayan Obo deposit is the largest comprehensive Fe-REE-Nb deposit in the world. The shape of ore bodies and the texture of ore are closely related to ductile structures. To understand the deformation characteristics and evolution of ore structures in the ore district, this study collected rocks for microscopic and Th-Pb geochronological analysis based on macroscopic structural analysis. Results show that rhombic, banded, and folded ore structures can be identified in the Bayan Obo deposit, which reflects gradually strengthening ductile deformation, involving minerals such as magnetite, monazite, fluorite, rare earth minerals, and dolomite. The most widely developed banded structures represent the products of ductile deformation of rocks during the compression stage. Selected syntectonic monazite gives a Th-Pb age of 432 ± 4 Ma, belonging to the Early Paleozoic. Referring to previous geochronological results in the Bayan Obo deposit, it is believed that this age represents the ductile deformation occurs at the Middle Silurian. In addition, the coarse-grained monazite shows an age range of 477 to 838 Ma and the geological significance represented by these ages is not yet clear. It may be related to the alteration of monazite during the mineralization by hydrothermal activity, resulting in a certain degree of lead loss. The U-Pb age of zircon in the undeformed diorite-porphyrite dyke is 274 ± 4 Ma, which constrains the upper limit of ductile deformation. Combining regional geological results, it is suggested that the Middle Silurian ductile deformation in the Bayan Obo deposit corresponds to the collage between the North China plate and the Bainaimiao arc. The intense collision has transformed the original ore-forming structure from both macro- and microscopic aspects, forming the existing pattern.
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Study on quality evaluation method of typical vein quartz deposits in Dabieshan area

Xiao Ying, Deng Yufeng, Ma Jinhai, Shen Huanxi, Zhan Jianhua, He Zhenzhong, Zhu Chuanhai, Hao Wenjun

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The Dabieshan area in China is characterized by the widespread occurrences of Mesozoic metamorphism and magmatism, with abundant vein quartz resources, which may become one of the key regions for strategic mineral exploration of high-purity quartz (raw material) in China. This paper determines the quality grades of high-purity quartz vein quartz samples from the Hongjiawan mineral occurrence and Baishishan deposits in the Dabieshan area. A comparative analysis is conducted based on factors such as hand specimens, fluid inclusions, content and occurrence states of impurity element in the ores with different quality grades, to identify typical quality evaluation indicators for vein-quartz ores in the Dabieshan area. The content of SiO2 in the processed quartz sand from Hongjiawan and Baishishan vein-quartz ores can reach 99.9971% and 99.9968% respectively, which meets the quality requirements of middle and high-end products. The quality of the Hongjiawan ore is better than that of the Baishishan ore. The comparative study of different quality of high purity quartz raw materials shows that, if the vein quartz is snow-white in color, higher transparency, larger fluid inclusion sizes dominated by two-phase (liquid-vapor) primary fluid inclusions, and lower impurity elements content, the quartz has the greater probability of becoming high purity quartz raw materials. The contents of impurity elements in recrystallized quartz and core of quartz veins are generally low, thus we should pay more attention to this part of quartz. This conclusion has a significance for evaluating the potential resources of high purity quartz raw materials in this area and clarifying the geological characteristics of future prospecting targets.
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Control of faults on hydrocarbon migration and accumulation of Baiyun North Slope in the Pearl River Mouth Basin

Ji Ruiyun, Qiu Nansheng, Chang Jian, Wang Xudong, Chen Cong, Li Kongsen, Chen Ran

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The hydrocarbon distribution in of Baiyun north slope in Pearl River Mouth Basin gradually rises from sag to slope, and the faults control the process of hydrocarbon migration and accumulation. Based on seismic data, we classify faults and evaluate the effects of faults on hydrocarbon migration and shielding. Combined with the distribution of hydrocarbon, three fault-controlled accumulation models are established, and the process of hydrocarbon migration and accumulation in Baiyun north slope is clarified. The source fault controls the vertical migration of hydrocarbon generated by the source rock in the depression area, and some hydrocarbon are accumulated in the multilayer series above the source. Key regulating faults control the migration of hydrocarbon from the Zhujiang Formation to the shallow Hanjiang Formation and Yuehai Formation. The key area for vertical regulation of oil and gas is near the P3 structure in the slope area, and the hydrocarbon in the H6 and H3 structures far from source have all been adjusted to shallow layers. Partial regulating faults in the slope control trap formation, the same fault can control the formation of multi-layer traps in the Zhujiang Formation, Hanjiang Formation and Yuehai Formation, and block the lateral migration of hydrocarbon accumulation. The hanging-wall mudstone of the reverse fault is connected with the foothall sandstone, and the sealing works well. Through the fault-control models and reservoir characteristics, it is concluded that P3 and H5 Zhujiang Formation reservoirs in the north slope of Baiyun have the characteristics of dynamic accumulation and dispersion, and hydrocarbon charging and vertical fracture leakage were carried out simultaneously in the late stage of accumulation. Finally, the reservoir formation model of effective hydrocarbon expulsion, regulating fault controlling shallow gas migration and accumulation, and reverse fault blocking accumulation in Baiyun north slope were established.
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Activity time constraint of NEE-trending strike-slip faults in southwestern Ordos Basin

Wang Huilong, Huang Lei

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A large number of faults are developed in the southwest of Ordos Basin. The determination of fault activity time is very important to clarify its relationship with oil and gas accumulation. However, there is no definite understanding of these fault activity periods. Based on field investigation and three-dimensional seismic data analysis, this paper analyzes the NEE-trending faults developed in the Jurassic-Cretaceous of the Mesozoic, and uses the laser in-situ U-Pb dating method of calcite veins in the fault zone to analyze the fault activity time. The results show that the two ages of the syntectonic calcite veins in the NEE-trending fault are (125.3±1.9)Ma and (79.04±0.68)Ma, respectively.Combined with seismic data interpretation, it is comprehensively limited that the fault is mainly developed in the late Early Cretaceous-Late Cretaceous. The age of the two-stage fault activity corresponds to the two overall uplift time (170-120Ma) and (80-60Ma) of the Ordos Basin since the Early Cretaceous, indicating that the multi-stage fault activity and the overall uplift since the Early Cretaceous have a corresponding relationship. The time of NEE-trending fault activity corresponds to the main accumulation period of early Cretaceous oil and gas in the study area and the adjustment period of late Cretaceous reservoir. The influence of NEE-trending fault activity on oil and gas accumulation is mainly reflected in the communication between source kitchen and reservoir and the transformation and adjustment of primary reservoir. According to the quantitative calculation results of formation pressure relief caused by the overall uplift of the study area, the development of these faults is also an important reason for the abnormal low pressure of the reservoir in the basin.
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Comparison of the Geochemical Characteristics and Genesis of Brine-Type Lithium Deposits in the Central and Western Qaidam Basin

Li Xiangjun, Yan Lingqin, Wang Zhendong, Shi Haiyan, Shi Zhen, Li Caiyun, Xue Hengtao, Yu Xiaoliang, Ma Ying

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Abundant brine lithium resources exist in the Qaidam Basin, presenting a favorable prospect of exploitation and utilization. As the two most significant types of lithium brine in the Qaidam Basin, the salt lake brine in the central area of the basin and the structural fissure-pore brine in the western anticlinal structures of the basin are examined. The hydrochemical characteristics of them were compared and analyzed. Based on the systematic analysis of ion correlation, ion characteristic coefficient, and H-O and B isotope composition, the causes thereof are discussed. Studies have indicated that there are marked differences in hydrochemistry between the two types of brines. The salt lake brine presented a relatively high average total dissolved solid content (320.1 g/L) and LiCl content (1378.33 mg/L), while the major ions were relatively abundant in K+, Mg2+, SO2- 4 and deficient in Ca2+. The average total dissolved solid (186.4 g/L) and LiCl content (376.04 mg/L) of the structural fissure-pore brine are relatively low. Meanwhile, significant differences exist in different anticlinal tectonic regions. The ionic components are relatively abundant in Ca2+ and deficient in K+, Mg2+, SO2- 4. The analysis of ion correlation, ion characteristic coefficient, H-O and B isotopes suggests that the two types of brines might have the same origin and have undergone distinct evolutionary processes, which are the two remnants of the evolutionary decline of the ancient lake in Qaidam. Salt lake brine is the evaporation residual brine. With the migration and evolution of the ancient salt lake, salt lake brine underwent continuous evaporation and concentration, and eventually enriched and formed in the central basin. The structural fissure-pore brine is the secondary salt lake brine that was sealed during the disintegration of the ancient lake, and it undergoes the transformation of leaching after being sealed, thus having the dual genetic characteristics of evaporation residual brine and leaching brine.The disparity in the evolution process of the two types of lithium brine gave rise to different brine lithium resource endowments in the Qaidam Basin.
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U-Pb age characteristics and geological significance of the detrital zircon in the sediments of the Songhua River, Jilin Province

NI Qian, GUO Lingfen, XIE Yuanyun, SUN Lei, CHI Yunping, LIU Haijin, WEI Zhenyu, WANG Yehui, WU Peng

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Rivers play an important role in the source-sink system, and their sediments are the key entry point for the provenance analysis of the source-sink system. The U-Pb age of river detrital zircon has been widely used in the study of drainage evolution, provenance tracing and source-sink. However, the factors influencing the U-Pb age distribution of fluvial-detrital zircons in high latitudes and their representation in provenance tracing studies have not been fully evaluated, which may lead to inconsistent results and further affect the establishment of source-sink systems..In this paper, the Jilin section of Songhua River was selected as the research object, and a total of 780 zircon U-Pb ages were analyzed from 6 river sediments, and quantitative constraints were applied by inverse Monte Carlo model.The results show that the zircon U-Pb age distribution mainly has three peaks: 2500Ma, 250Ma and 180Ma, and the age distribution pattern of zircon changes significantly from upstream to downstream.Among them, the proportion of zircons with characteristic age of 2500Ma from the northeast margin of North China Craton in the upper and middle reaches has decreased significantly, suggesting that the increased contribution of new provenance in the middle reaches has diluted the provenance signal in the upper reaches, and may also be related to the interception effect of Fengman Reservoir.The contribution proportion of the northeast margin of the North China Craton in the middle to lower reaches continues to decline, and the contribution of the Songnen and Zhangguangcai Range blocks increases, indicating the addition of new provenance during river transport.In the main stream of the Songhua River, a large number of zircon particles smaller than 250Ma brought by the Nenjiang River dilute the age characteristics of the second Songhua River zircon at 2500Ma.In the study of source-sink system, the provenance signals in different river reaches are different, and even the provenance signals in the upper reaches may be missing in the lower reaches, so there is some uncertainty in using detrital zircon age data from river estuaries or a single sample to represent the provenance information of the whole catchment.In addition, the peak age of the Jilin section of Songhua River is in good agreement with the tectono-magmatic thermal event of the eastern Central Asian orogenic belt. 2500Ma May be the record of the consolidation of the North China Craton microlandmass, and 250Ma and 180Ma are in response to the closing of the Paleo-Asian Ocean and the subduction of the Paleo-Pacific plate, respectively.This study is of great significance for understanding the sourcing-sink process in the Jilin section of Songhua River, and also provides important reference value for tectonic events in Northeast China.
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XRF element and infrared spectrum characteristics of Luzong scientific drill

zhaolongxian, shi weixing, yuan chunyu, zhang hong, li zhenhuang, guo dongxu, hui guangji, ge tianzhu

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The Lu-Zhong Mining District, situated within the Middle-Lower Yangtze River Metallogenic Belt, is significant for its polymetallic and granitic-hosted uranium deposits. This study presents the first discovery of high-temperature uranium mineralization through scientific deep drilling in the district. Utilizing shortwave to thermal infrared (SWIR-TIR) spectroscopy, X-ray fluorescence (XRF) elemental analysis, and electron microprobe techniques, we systematically analyzed the mineral distribution, ferromagnesian mineral variations using the FMI, and the spectroscopic and compositional characteristics of chlorite.Our findings indicate that infrared spectroscopy effectively identifies minerals in volcanic and igneous rocks. The FMI from TIR spectra reliably distinguishes relative changes in ferromagnesian content, aiding in lithological differentiation and understanding ore-forming environments. XRF data provide valuable insights into the major and trace element trends within the drill core.Chlorites in the drill core are classified as disseminated, sheet-like, and veinlet-distributed, primarily consisting of clinochlore and penninite, with all types being trioctahedral. Disseminated and sheet-like chlorites formed at higher temperatures (300-349°C) compared to veinlet-distributed chlorites (190-324°C). The Pos2250 feature in chlorite infrared spectra ranges from 2245nm to 2257nm without a clear trend throughout the core.Notably, this study proposes that the presence of chlorites with wavelengths less than 2248.8nm at depth may indicate high-temperature uranium-thorium mineralization in the Lu-Zhong district, providing a new indicator for exploration.
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Apatite Fission Track Spatial Distribution Characteristics: Implications for the Evolution of Tectono-geomorphological Landscapes — A Case Study of Wugongshan

Gao Shangyan, Li Guangwei, Zhang Yuwei, Ye Zhanghuang

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The evolution of landforms is controlled by the interaction between tectonic activities and surface processes, and exploring the contribution of both to the evolution of structural geomorphology has always been a hot and difficult point in the study of the evolution of orogenic geomorphology. In recent years, the rapidly developing low-temperature thermochronology has become a powerful method for studying the quantitative evolution of tectonic geomorphology. Therefore, this study uses low-temperature thermochronology method to investigate the exhumation processes and mechanisms of the typical granite gneiss dome in China - Jiangxi Wugong Mountain. We targeted the core of the Wugong Mountain range - the north and south sections of Mingyue Mountain for sampling and conducted apatite fission track analysis. The apatite fission track ages are mainly concentrated at ~65-42 Ma, and the ages on both sides of the mountain show a clear negative correlation with elevation. This may be due to the fact that the exhumation of the Wugong Mountain dome in the Late Cretaceous were mainly controlled by the detachment faults on both sides, while the denudation process in the Cenozoic was mainly affected by surface erosion. This indicates that for relatively old orogenic belts, the spatial distribution characteristics of low-temperature thermochronology ages can be used as an indicator to discern the main control mechanisms of tectonic geomorphological evolution. In addition, according to our thermal history simulation results, the Wugong Mountain area has experienced a rapid exhumation stage in the Late Cretaceous, a slow stage from the Paleocene to the early Miocene, and a relatively rapid exhumation stage since the early Miocene, mainly controlled by regional tectonic activities and climate change, respectively.
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Evolution characteristics of marine nitrogen cycle and redox structure during early Cambrian in the western Hubei aulacogen of middle Yangtze Block

Meng Kang, Hu Yunpeng, Zhang Yu, Shao Deyong, Tang Lei, Song Hui, Zhang Tongwei

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The evolution characteristic of marine redox structure during early Cambrian in the western Hubei aulacogen of middle Yangtze Block is still unclear. In this study, the Lower Cambrian shales of well LX03 in the western Hubei aulacogen were taken as the research object. Firstly, origins of differences in nitrogen isotope compositions of whole rock and kerogen were analyzed to determine which nitrogen isotope was suitable for characterizing the marine redox environment at that time. On this basis, the dynamic evolution process of marine nitrogen cycle and redox structure during the deposition of Lower Cambrian Shuijingtuo organic-rich strata in this area was reconstructed by further integrating redox-sensitive elements and benthic foraminifera. The results showed that biological assimilation occurring in anoxic pore water during sedimentation and early diagenesis stages leaded to nitrogen isotope fractionation between kerogen and silicate minerals. However, this process took place within a relatively closed system and had minimal impact on the whole rock nitrogen isotope (δ15Nbulk). Moreover, the δ15Nbulk was not affected by secondary processes such as terrestrial input, microbial degradation, thermal maturation, and metamorphism, making it a reliable geochemical indicator for reconstructing the marine redox structure during the deposition of organic-rich sediments. During the deposition of the lower part of first member of Lower Cambrian Shuijingtuo Formation, the redox interface was located at the marine’s surface, with marine primarily characterized by euxinic condition (limited NO3- pool), and organisms acquired nitrogen mainly through nitrogen fixation. When the upper part of first member and lower part of second member of Lower Cambrian Shuijingtuo Formation deposited, the redox interface descended, with the upper oxic water expanded (enlarged NO3- pool), and organisms acquired nitrogen increasingly through the less energy-consuming NO3- assimilation process. During the deposition of the upper part of second member of Lower Cambrian Shuijingtuo Formation, the upper oxic water further expanded, and the bottom water transitioned to a low-oxygen environment. The low-oxygen bottom water promoted the proliferation of benthic foraminifera and other ancient organisms adapted to extreme low-oxygen conditions, with NO3- assimilation becoming the primary pathway for organisms to acquire nitrogen.
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The indicative significance of mica minerals to the genesis of Dangba pegmatite-type lithium deposit, western Sichuan, China

Zhao Yuan, Ran Fengqin, Tang Juxing, Peng Bo, Yang Yang, Han Jingrui, Feng Dabo, Bai Yun, Dai Yongkun, Tian Songlin

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Located in the Songpan-Ganzi orogenic belt, the Keeryin ore field is one of the important pegmatitetype lithium ore concentration areas in China. The Dangba deposit is a super-large pegmatite lithium deposit in the ore field. For a long time, it has been considered that the two-mica monzonitic granite in the Keeryin area is the main ore-forming parent rock of lithium mineralized pegmatite in this area. In order to further reveal the evolutionprocess of Dangba pegmatite and the enrichment mechanism of rare metals, mica, a penetrating mineral in granite and pegmatite, was selected as the research object in this paper. Based on previous studies, detailed rock and mineral identification, electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis were carried out. The results show that: ①The mica series in the Keeryin two-mica monzonitic granite and Dangba pegmatite show the evolution trend of muscovite → iron-lithium mica → lithium mica, and 4AlTot?3SiIV+□VI and 3LiVI?AlVI+2□VI are the dominant substitution mechanism of this process; ② The muscovite series in the Keeryin two-mica monzonitic granite and Dangba pegmatite show theevolution trend of muscovite → iron-lithium mica→ lithium mica.The high degree of crystallization differentiation process of Dangba pegmatite, the initial melt rich in Li and the late fluid relatively poor in F, and the relatively weak scale of fluid action are of great significance for lithium mineralization.
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Analysis of Ore-Controlling Structure of Lujing Uranium Ore Field in Hunan-Jiangxi Border

Chen Bailin, Pei Yingru

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Analysis of Ore-Controlling Structure of Lujing Uranium Ore Field in Hunan-Jiangxi Border Chen Bailin Institute of Geomechanics，Chinese Academy of Geological Sciences，Beijing 100081，China Lujing uranium ore field is one of the most important hard-rock uranium ore fields in South China. There are many small uranium deposits and occurrences such as Lujing large uranium deposit (322), Shabazi (327), Gaoxi (326), Huangfengling (325) and Niuweiling (324). The surrounding rocks of uranium ore bodies in the ore field are Mesozoic granite and Cambrian shallow metamorphic clastic rocks. Uranium ore bodies in granite are controlled by NNE(NE)-oriented faults (a little NEE-oriented), while uranium ore bodies in shallow metamorphic clastic rocks are controlled by NWW (near east-west)-oriented faults. The ore-guiding structure of the ore field is the regional extensional tectonic environment and its related magmatic activity and rock intrusion structure; Ore-matching (transporting) structure is a high-angle normal fault and rock mass emplacement structure which is connected with deep gas-liquid thermal fluid, and its upper part is connected with ore-bearing structures in different directions. Ore-bearing structures can be structural traces formed during mineralization, structural traces formed before mineralization and active structures during mineralization, while ore-controlling structures must be those during mineralization. The ore field structure has gone through nine stages: basement fold formation, Indosinian intrusion, early Yanshan intrusion, NNE-trending ore-bearing structure formation in the late early Cretaceous, EW-trending basic dike intrusion in the late early Cretaceous, uranium mineralization in the late early Cretaceous-early late Cretaceous, uplift and denudation in the early late Cretaceous, red bed basin covering and burial in the late Cretaceous-early Paleogene, and uplift and denudation since the middle Paleogene. There is no necessary genetic relationship between Fengzhou red bed basin and uranium mineralization, and it plays a role in protecting uranium deposits formed earlier than it. The favorable areas for further prospecting are Fengshuxia-Niuweiling-Jiaoyelong-Shabazi area and Dachangping-Dongfangzi-Lujing-Miaobeilong area covered by Fengzhou red bed basin. Key words: ore-controlling structure; ore-bearing structure; further prospecting for uranium deposits; Lujing uranium ore field; Hunan-Jiangxi Border.
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Petrogenesis and geological significance of Late Carboniferous strongly peraluminous granite in West Junggar

DUAN Fenghao, ZHI Qian, LI Wei, PENG Nanhe, WANG Qian, WANG Panlong, FU Hao, Zhang Jianye

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The intermediate-acid intrusive rocks exposed in the West Junggar, southwestern segment of the Central Asian Orogenic Belt, are mainly metaluminous to weakly peraluminous I-type and A-type granites. This study presents petrological, zircon U-Pb geochronological and in-situ Hf isotopic, whole-rock geochemical data of the newly discovered primary-muscovite-bearing strongly peraluminous granites in the Azhaken area. Petrographic observation results show that the strong peraluminous granites are mainly composed of muscovite monzonitic granite porphyry, two-mica monzonitic granite, muscovite granite and granite porphyry. LA-ICP-MS zircon U-Pb dating reveals middle Late Carboniferous magmatism with age of 309.1±3.8 Ma, later than metaluminous I-type granites (322~310 Ma) but slightly earlier than weakly peraluminous A-type granites (307~294 Ma) in the region. It is geochemically characterized by enriched silicon, aluminum, but depleted calcium, ferrum and magnesium, and possesses high total alkali content and aluminum saturation index (A/CNK=1.06~1.24, 1.14 in average), and also enrichment in Ba, Rb, K, Th, U with pronouneed negative Nb, Ta and Ti anomalies. In addition, it is characterized by corundum content of 0.85%~2.83% (1.79% in average) and absence of diopside showed through CIPW standard mineral calculation, indicating that they are strongly peraluminous high-K calc-alkaline S-type granite. In-situ zircon Hf isotope analyses show that these granites have high positive εHf(t) values (+10.8~+15.6) and very young two-stage Hf model ages of 326~633 Ma, suggesting that the magma was sourced from juvenile crust originated from depleted mantle. In association with previous analysis, it is proposed that the newly discovered middle Late Carboniferous strongly peraluminous S-type granites were probably originated from muscovite dehydration melting of metapelites under the water-absent condition during the initial transformation from extrusion to extension regime in the rapid collage process of subduction accretion bodies under the background of northwestward subduction of the Junggar oceanic crust.
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Indications of garnet to the age and environment of mineralization from the Pandian skarn－type Fe deposit in the Qihe－Yucheng area of Luxi, Shandong province

ZHU Xueqiang, WANG Laiming, HAO Xingzhong, QIN jie, YANG Zhenyi, YANG Shipeng, LI Fenghua, WANG Jinguang

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The Fe deposit in the Qihe－Yucheng area is a newly discovered skarn－type iron－rich deposit in the ultra－deep cover area in Luxi area of Shandong Province, which is closely related to the Early Cretaceous dioritic magmatism, but the age of mineralization has not been well qualified. In this paper, LA-ICP-MS U-Pb isotope dating, major and trace elements analysis, hydrogen－oxygen stable isotope analysis and mineral inclusions analysis were carried out on garnet from the Pandian skarn－type Fe deposit. Garnet is mainly composed of andradite ( And = 55.55 % ~ 74.24 % ) and grossular ( Gro = 22.16 % ~ 40.05 % ), belonging to grossular－andradite series. The garnet Tera－Wasserburg diagram of the two skarn samples shows that the lower intersection ages are 122.8 ± 3.4 Ma and 123.7 ± 9 Ma, belonging to the Early Cretaceous. The rare earth compositions generally show a left－dipping type with light rare earth elements loss and heavy rare earth elements relative enrichment, with obvious Eu positive anomaliy. The inclusions are mainly molten inclusions, containing iron components such as hematite and iron complexes. The value of δDV－SMOW of inclusions is －69.50‰~－88.30‰, and the value of δ¹⁸OH2O is 8.43‰~12.21‰, which belongs to magmatic water. Comprehensive analysis suggests that the Pandian Fe deposit in the Qihe－Yucheng area is the product of the peak period of thinning and destruction of the North China Craton in the early Early Cretaceous. The ore－forming fluid is derived from the iron－rich high－temperature magmatic hydrothermal, in which the slightly acidic neutral and oxidizing environment provided conditions for the unloading and mineralization of Fe.
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Sedimentary geochemistry of Mesozoic cherts in Tongjiang area of Northeast China: Implication on the subduction of Paleo-Pacific subduction

ZHANGWenHao, ZHOU Jianbo, ZHOU Xingui, WANG Dandan, LIU Weibin, Meng Yuanlin, LIU Xufeng

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The Sanjiang area in Northeast China hosts the sole exposed Mesozoic siliceous rock series in northern China, which holds significant geochemical characteristics for unraveling its genesis and tectonic setting, particularly to trace the temporal and spatial initiation of paleo-Pacific subduction. In the Tongjiang area north of Sanjiang, the "Heitongdi 1 Well" reveals a silicic rock system from the late Triassic to Early Jurassic Dajiashan Formation, spanning approximately 400 meters. Through field geological investigation, microscopic observation, and petrogeochemical analysis of core samples from this well, we have conducted a comprehensive study on the origin and tectonic environment of these siliceous rocks. Radiolarian fossils are observed in the siliceous rocks of the Tongjiang area. The mean Al/(Al+Fe+Mn) value in the siliceous rock samples was 0.74, with no discernible Ce anomaly and Ce/Ce* values ranging from 1.02 to 1.54, (La/Ce)_SN≈1, no significant difference in Y/Ho values, a mean Y/Ho value of 30.02, and a mean Eu/Eu* value of 1.17, indicating that these siliceous rocks were formed in a continental margin island arc environment. The present study also provides compelling evidence for the initiation of subduction of the Paleo-Pacific plate beneath the Eurasian plate during the late Triassic period, leading to the establishment of an island arc environment along the eastern margin of Jiamusi Block. The inferred location of the subduction suture between these two plates is situated westward from Tongjiang drilling hole.
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Implications of paleoproterozoic regenerated granites on Precambrian tectonic evolution in the southwest margin of the Yangtze block

zhanghonghui, yuanyongsheng, zhenghongfu, liujunping

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The southwest margin of the Yangtze Block played an important role in the amalgamation and fragmentation processes of the Columbia supercontinent, but the tectomagmatic evolution of the late Paleoproterozoic is insufficient and controversial. In this study, Paleoproterozoic regenerated granite was found in Lufeng area of central Yunnan Province, southwest margin of Yangtze Block. It was formed by the rapid sedimentation of weathered K-feldspar granites within the Paleoproterozoic Lüzhijiang Formation. The main components are quartz, potassium feldspar, a small amount of biotite and plagioclase. LA-ICP MS zircon U-Pb dating, Lu-Hf isotope, rock geochemistry and zircon trace element analysis showed that: the weighted average 206Pb/207Pb age of zircons is 1849±6Ma (MSWD=0.11, n=21). The εHf(t) values of 7 zircons range from -7.23 ± 0.7 to -3.58 ± 0.75, with an average of -5.2 ± 1.2, and the TDM2 is 2819±73Ma. The trace element characteristics of zircons and petrogeochemical features indicate that the protolith was S-type granite, possibly derived from the melting of metasedimentary rocks in the Middle Archean. The discovery of Paleoproterozoic regenerated granites indicates the existence of S-type granites of ~1.85Ga in the southwest margin of the Yangtze block, providing a new evidence for the tectonic chronology and petrology of the Columbia supercontinent. It also shows that the formation of Lüzhijiang Formation in central Yunnan Province is Paleoproterozoic, providing new data for the Precambrian geological research in central Yunnan Province.
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Ordered distribution and reservoir characteristics of Lower Permian sedimentary rocks in Junggar Basin

Zheng Menglin, Wangran, Chang Qiusheng, Qin Zhijun, Wang Tao, He Wenjun, Guo huajun, Zou Yang, Sun Jing, Wu Haisheng, Shan Xiang

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Mahu Sag is an important example of the application of the theory of the whole oil and gas system, Junggar Basin. The oil-gas reservoir pattern with normal and irregular distribution corresponds to the reservoir type with orderly distribution. In order to clarify its reservoir characteristics and control factors, the drilling, logging, analysis and laboratory analysis data of more than 50 Permian reservoirs in Mahu Sag are analyzed. The Permian sedimentary rock reservoirs in Mahu Sag are characterized by orderly lithology, facies and reservoir property from the edge of the sag to the depositional center. The lithology develops coarse clastic rocks, medium clastic rocks and fine-grained sedimentary rocks successively, and the grain size changes from coarse to fine in an orderly, continuous and sequential manner, which corresponds to the sedimentary facies changes. Coarse clastic rocks can be divided into rich shale conglomerate facies, shale conglomerate facies and lean shale conglomerate facies according to the level of shale content. Fine-grained sedimentary rocks can be divided into argillaceous lithofacies and dolomitic lithofacies according to the content of felsic and livid. The lean and argillaceous conglomerate facies and argillaceous rock facies have good reservoir property, and large-scale conventional conglomerate and unconventional shale oil reservoirs have been found respectively. Sedimentary facies control the orderly distribution of lithology, and gravity flow, torrent, traction flow, heavy flow and light flow dynamic fluid are closely related to the orderly distribution of lithofacies. The content of argillaceous complex and the composition of felsic mineral have decisive influence on the reservoir property of coarse clastic rock and fine grained sedimentary rock, respectively, and compaction diagenesis has important influence on the reservoir property of medium clastic rock. The orderly distribution of sedimentary rocks and the regularity of their reservoir properties control the gradual transition of oil and gas from continuous unconventional reservoirs to discontinuous conventional reservoirs.
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Sequence-Stratigraphy-Filling and Reservoir-Cap rock Assemblage Distribution Under the Control of Lake Basin Types: A Case Study of the Fengcheng and Baikouquan Formations in the Mahu Sag, Junggar Basin

zhangbao, Yan Detian, Tongyong, Zheng Menglin, Chang Qiusheng, Wei Xiaosong, Zhang Lei, Bai Yu, Yu xing

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The Junggar Basin, as one of China's important oil and gas production areas, contains abundant petroleum reserves. However, research on the basin's lake basin evolution is relatively limited, particularly regarding the relationship between lake basin types and the distribution of reservoir-cap rock assemblage during the Permian to Triassic deposition.This study, based on sequence stratigraphy frameworks, integrates structural evolution and paleoclimatic characteristics to systematically analyze the control of lake basin types on sequence-stratigraphy-filling and the distribution of reservoir-cap rock assemblage in the Junggar Basin. The results show that the Permian-Triassic sequence in the northwestern margin of the Junggar Basin has been divided into three supersequence (SSQ1-SSQ3) and eight third-order sequences (SQ1-SQ8). SQ2 is subdivided into the rift initiation system tract, rift climax system tract, and post-rift system tract. SQ6 is subdivided into the falling-stage systems tract, the lowstand system tract, expansion system tract, and the highstand system tract. The deposition period of SQ2 characterizes a typical underfilled discharge (UF-D) lake basin, where high-quality reservoirs mainly develop in the rift climax system tract, characterized by conglomerates and sandstones with residual intergranular pores and dissolution pores, resulting in relatively high porosity. The source rocks exhibit high productivity, conditions of high anoxic preservation, and weak dilution. The distribution of the Fengcheng Formation's reservoirs and source rocks is controlled by fault activities accompanied by the input of hydrothermal fluids and arid conditions induced by the Late Paleozoic glaciation.During the SQ6 deposition period, a typical overfilled lake basin is represented, with high-quality reservoirs mainly developing in the forced regressive and lake expansion system tracts, primarily consisting of sandstones. Continuous lake wave reworking and intermittent exposure increased porosity. The primary source of hydrocarbons is the SQ5 source rock, characterized by high productivity, poor preservation conditions, and strong dilution. The distribution of the Baikouquan Formation's reservoirs is controlled by tectonic uplift during the late Hercynian orogeny, the arid paleoclimate conditions of the Permian-Triassic transition, and the subsequent continuous lake transgression. This study reveals the sedimentary evolution patterns of the Permian to Triassic strata in the northwestern Junggar Basin, particularly the sequence-stratigraphy-filling characteristics and reservoir-cap rock assemblage distribution controlled by lake basin types. The findings provide important references for the study of lake basins with similar structural and climatic settings and have significant implications for oil and gas exploration.
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Establishment of the southern margin fault zone of Bogda and its geological significance

Zhang Jianye, Li Yongjun, Zheng Menglin, Wang Tao, Li Wei, Wang Qian

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The boundary between the Bogda stratigraphic minor-region and its neighbor, the Yilianhabierga stratigraphic minor-region, has been in dispute for a long time, and the corresponding boundary of the two tectonic units have also been disputed. Determining the contact relationships between the lithostratigraphic units in the Bogda region is the key to answering the aforementioned scientific questions. The southern margin fault of Bogda has discovered and established in Bogda area in this study, it’s a large-scale and stable extension, belonging to the levitra strike-slip fault, which was hidden in the Tuha Basin and Junggar Basin on the south and north sides, respectively. Detailed field geological investigations and refined comparisons of previous research results show that the geologic entities of the northern and southern plate of the fault have different deformation histories, sedimentary histories, and histories of magmatic activity and tectonic evolution. Detrital zircons indicates different source compositions and geological background of contemporaneous terrigenous clastic rocks in Late Carboniferous on both sides of the fault, implying that the two sets of upper Carboniferous units belong to two sedimentary basins. It is shown that the southern margin fault of Bogda has the basic property of dividing the stratigraphic minor-region. The establishment of the southern margin fault of Bogda effectively defines the boundary between Bogda stratigraphic minor-region and the Yilianhabierga stratigraphic minor-region, new information is provided for the research of zonal stratigraphic grids.
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Research progress and exploration application of Tectono-geochemistry in the recent decade

CHENG Yongsheng, ZENG Dexing

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On the background of the demand for deep mineral exploration, tectono-geochemistry has distinct advantages over soil and rock geochemistry in predicting hidden minerals, which has aroused the research interest of domestic and foreign scholars. This article summarizes the research progress on concepts and theories as well as exploration application results of tectono-geochemistry, leading to the following understandings: 1) Tectono-geochemistry is an emerging interdisciplinary subject that explores the intrinsic relationship between tectonic dynamics and geochemical substances and studies the behavior and results of material components in tectonic processes. 2) Tectonic action controls the physical and chemical properties of material activation in geological space, drives the migration of materials in tectonic fluids, and ultimately leads to the differentiation and enrichment of elements. 3) Tectono-geochemistry has made significant research progress in terms of "Tectonically driven geochemistry," "geochemically induced structural deformation," and "geochemical dynamic process simulation," but the "dynamic mechanism" still needs further exploration. 4) The workflow of tectono-geochemistry exploration applications includes structural analysis, structural sampling, statistical analysis of element combinations, anomaly interpretation, mineralization model construction, and target area delineation. 5) The application of tectono-geochemistry in ore deposit exploration has achieved remarkable results, including polymetallic deposits of Cu, Au, Pb, Zn, Ag, Mo, Sb, Sn, etc. Foreign scholars tend to study the mineralization mechanisms and mineralization models, while Chinese scholars focus on deep predictions and target area delineation of ore bodies. In addition, the rich deep-seated, three-dimensional, and multi-media sampling, the application of big data and machine learning methods in data analysis, and the verification of ore body spatial distribution by short-wave infrared are all future development trends of tectono-geochemistry exploration, with great research potential and broad application prospects.
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Permian paleogeographic differentiation evolution and platform margin model comparison in Sichuan Basin

Li Wen, Chen Anqing, Zhang Xihua, Sun Shi, Huang Huiwen, Gao Zhaolong, Xu Shenglin, Huang Ganghui, Xie Hao, Yang Shuai, Chen Hongde

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The carbonate platform margin is an important gathering place of large-scale oil and gas resources, and the study of paleogeographic differentiation is the basis to reveal the characteristics and development laws of the carbonate platform margin. Following the discovery of a trillion square meter natural gas gold accumulation zone in the platform margin reef-beach facies of the Upper Permian Changxing Formation in Sichuan Basin, the platform margin beach reservoir of the Middle Permian Maokou Formation has recently been discovered, and several open flow wells of more than one million square meters have shown great exploration potential. However, there are significant differences in sedimentary filling and reservoir characteristics between these two periods, and detailed comparative analysis will help deepen the understanding of carbonate platform model and its reservoir control effect. Based on a large number of drilling, field outcrop and seismic data from the Sichuan Basin and its surrounding Permian system, the typical sedimentary facies and lithofacies paleogeographic pattern are analyzed, and the differences between the two types of platform margins are compared. The results show the differentiation from shallow-water platform to deep water shelf by multiple synsedimentary faults occurred in Permian paleogeography of Sichuan Basin from Maokou period, with Kaijiang-Liangping trough being the most typical. The shallow-water carbonate platform of Changxing Formation is characterized by the development of thick platform margin reef-beach facies, and the shallow-water carbonate platform of Maokou Formation is characterized by the development of thin platform margin beach facies, both of which rapidly change into siliceous rock and carbonaceous shale. The Maokou period belongs to the initial geomorphic inherited platform margin, which is represented by several thin beach bodies with intermittent accretion under the background of wide margin. In the Changxing period, the platform margin was shaped by sedimentary border, showing a thick reef flat body with continuous accretion or prograding under the background of narrow margin. In general, both platform margins have the potential to develop large-scale reservoirs and are important targets for exploration of large oil and gas accumulation zones.
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Provenance characteristics of the Yangjiazhuang Formation on Tianheng Island: constraints from detrital zircon U-Pb dating and whole-rock geochemistry

MENG Yuanku, Yang Shubo, Yang Peng, Meng Fanxue, Lu Jie, Gao Cunshan, Li Zhaoying, Wang Zhenzhen

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The Jiaolai basin was formed in the rapid exhumation processes of the Sulu orogenic belt and Jiaobei terrane. Its evolutionary processes played a key role in constraining exhumation and denudation of the Sulu orogenic belt and Jiaobei terrane and destruction of the north China Craton (NCC). In this work, we took the Yangjiazhuang Formation of the Laiyang Group, which is located in the eastern margin of the Jiaolai Basin, as the research target to carry out systematic field geological survey, petrographic analyses, detrital zircon U-Pb dating and whole rock element measurements. Based on the systematic studies on the Yangjiazhuang Formation, we can draw the following conclusions: (1) the sedimentary age of the Yangjiazhuang Formation is well-defined between 125 and 115 Ma, belonging to the Apian stage of the Early Cretaceous; (2) the geochemical features of the mudstone revealed that provenance of the Yangjiazhuang Formation experienced relatively weak chemical weathering, and primary sedimentation played a key role, and the upper continental crustal (UCC) materials were the dominant provenance; (3) change of the sedimentary provenance of the Yangjiazhuang Formation and diversities indicated that the Jiaobei terrane was the other important provenance during the middle-late stages of sedimentaion besides the Sulu orogenic belt. Combined with the regional tectonic background, we propose that the rapid uplift and exhumation of the Sulu orogenic belt and Jiaobei terrane might have a close relationship with the crustal large-scale extension and thinning due to the destruction of the NCC.
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Fine Study on the Characteristics and Evolution Process of Typical Evaporite StrataExposed in the Kuqa Basin, Xinjiang

YANG Sibo, XU Yang, LIU Chenglin, MO Tao, YAO Kun, FAN Kunyu, ZENG Xize, E Yuqi, LIU Lei

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Due to the salt tectonic diapirism, a large number of evaporite geological bodies are exposed on the surface of the Kuqa Basin, providing excellent materials for the study of evaporite strata. However, there has been a lack of detailed research on them before. This paper selects the typical Dawanqi salt dome and gypsum dome as the research objects, and reveals the salt-forming evolution law through various research methods such as X-ray diffraction (XRD) analysis, thin section identification, scanning electron microscopy and energy dispersive spectroscopy, geochemical analysis, and fluid inclusion homogenization temperature analysis. It is concluded that the gypsum rocks in the Late Eocene evaporites of the Kuqa Basin can be subdivided into 7 types, and the salt rocks widely develop regular mudstone-pebble structures. It is determined that the sedimentary environment of the Late Eocene evaporites in the Kuqa Basin belongs to the inland sabkha, and the temperature range of the brine during the salt-forming period is between 11.2 - 32.5 °C, with an average of 22.3 °C. In the early stage of the saline lake period, it experienced two episodes of concentrated brine seepage or disturbance, and after stabilization, it received two freshwater replenishments; the salt lake period experienced a total of five freshwater replenishments. In addition, it is found that the rhythmic alternation of gypsum and anhydrite deposits, as well as the rhythmic variations in the quantity and size of mudstone pebbles in salt rocks, can be used as indicators to judge the concentration and desalination of brine in the salt lake. This study provides a typical case for the sedimentary evolution of evaporites exposed in the Kuqa Basin and even in domestic salt basins.
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Current status and development trends of coverage area types and exploration techniques in China

Wang Qingsong, Yan Tingjie, Wang Yafei

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The covered area is an important exploration region for the new round of mineral discovery breakthroughs. The cover layer acts as a barrier to geophysical anomalies, presenting challenges in delineating exploration selection areas, defining mineral target zones, and locating deep mineral bodies. Based on mineral exploration theory, this paper analyzes the physical characteristics of the cover layer and the difficulties in mineral exploration by reviewing literature and combining it with practical experiences in covered areas. It systematically summarizes the current status and development trends of geophysical and geochemical exploration techniques in mineral discovery applications within covered areas, aiming to provide references for strategic actions in the new round of mineral discovery breakthroughs. The research indicates that the difficulty of mineral exploration in covered areas is not only related to the thickness of the cover layer but also closely linked to the physical characteristics of the cover layer and hydrogeological conditions. Accordingly, the covered area is classified into eight types: low-resistivity thin cover area, low-resistivity thick cover area, water-rich low-resistivity thick cover area, low-resistivity ultra-thick cover area, desert cover area, volcanic rock cover area, thrust fault cover area, and composite cover area. Among these, the low-resistivity thick cover area, water-rich low-resistivity thick cover area, and low-resistivity ultra-thick cover area present greater challenges for mineral exploration. The study shows that China has widely tested and applied geophysical and geochemical exploration techniques in thin cover areas, achieving significant results, and has also accumulated some experience in mineral exploration in thick cover areas, initially establishing various exploration technical systems for different mineral types in different covered areas. However, the challenges of delineating mineral target zones and detecting deep mineral bodies remain unresolved. Looking ahead, research on precise detection technologies that penetrate thick cover layers will be a key development direction, with geophysical electromagnetic methods and stimulated electric/magnetic field detection technologies expected to advance rapidly. The diversification of geological information collection methods across air, ground, and well platforms, along with the integration of comprehensive information processing and artificial intelligence in mineral prediction, will become an inevitable trend. The integration of geological and geophysical research on controlling mineral structures and mineralization models in covered areas will play an increasingly important role.
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A Preliminary Exploration of Active Fault Identification Methods in the Deep-cut River Valley Region: A Case Study of the Batang Fault

yuhao, zhong ning, zhang xianbing, yang zhen, yu xiao, wu ruian, wang yang, yang zhihua, guo changbao, li haibing

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The Batang fault is a significant seismogenic fault in the oblique-slip Jinsha River tectonic belt, which triggered the Batang earthquake with a magnitude of 7.25 in 1870. It is mainly distributed in the deep-cut river valley regions of the Jinsha River and Lancang River. Due to the large relief in the deep-cut river valley regions, frequent landslide and debris flow disasters, and well-developed vegetation, the fault traces are not clearly visible. As a result, there are differing interpretations regarding the geometric distribution and activity nature of the Batang fault. This article, based on high-precision remote sensing, unmanned aerial vehicle (UAV) photogrammetric measurement, geophysical exploration, paleoseismic records of ancient landslides and deposits, and precise earthquake location methods, further refines the geometric distribution and activity nature of the Batang fault. The research results suggest that the Batang fault is a Holocene active fault, predominantly characterized by right-lateral strike-slip motion with a component of thrusting. The southwestern extension of the Batang fault (referred to as the Naozhong Fault), forming a V-shaped fault with the Deqin-Zhongdian-Daju fault, may serve as the southwestern boundary fault of the Zhongdian secondary block. The tectonic stress field reveals that the Batang fault experiences primarily southwest-northeast compressional stress, accompanied by a certain northwest-southeast extensional component. This may be attributed to the eastward movement of the Qiangtang Block, clockwise rotation of the Zhongdian Block, and the southeastward escape of the eastern margin of the Tibetan Plateau. Finally, a preliminary summary of research methods for active faults in deep-cut river valley regions is provided, aiming to serve as a reference for the identification and investigation of active faults in such areas.
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The indicators of Muscovite and Feldspar to the Prospecting direction of Rare metal pegmatite——Constraint on the discovery of spodumene pegmatite in Yanlingguan, xintai city, central Shandong

LIU Qinlong, LI Jiankang, LI Peng, LI Yingjie, LI Shenghu

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The efficient prospecting and exploration indicators of rare metal pegmatite in the eastern high coverage area is still difficult. In order to study how to delineate the mineralized pegmatite in the rare metal pegmatite in the eastern high coverage area, this studies carried out the major and trace elements of muscovite and feldspar in Yanlingguan pegmatite group in Xintai city, Shandong Province, analyzed and delineated the favorable areas of rare metal pegmatite, determined the prospecting direction by using the elemental composition and mineralization index of muscovite and feldspar, successfully found lepidolite and spodumene, and calculated the crystallization temperature of Yanlingguan pegmatite group by using feldspar thermometer. The regional zonation of Yanlingguan pegmatite group is poor, with no obvious change in lithology and mineral composition. It can be divided into Taohuayu area in the south, Tianjingyu area in the middle and Yanlingguan area in the north. The K/Rb ratio and Li of mica and feldspar show that the pegmatite dikes in Yanlingguan area have undergone highly crystalline differentiation and evolution. The conclusion that Li-rich muscovite and Cs-rich feldspar can be used as indicator minerals for lithium mineralization in the eastern high coverage area is confirmed. According to the calculation of feldspar temperature, the temperature changes are very regular when the trondhjemite in Shanggang unit and Yanlingguan pegmatite field crystallize, so the trondhjemite is the ore-forming parent rock of Yanlingguan pegmatite field.
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Late Cenozoic Activity Characteristics of the Chenghai Fault Zone in the Qina-Binchuan Section and Its Implications for the Extrusion of the Sichuan-Yunnan Block

LI zhichao, Wu Zhonghai, Lu Haifeng, Huang Xiaolong, Song Xiyan, Yao Haitao, Huang Feipeng, Ceng Jing, Jiang Jiaqi

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The Chenghai Fault Zone, as the eastern boundary fault of the Dali Rift System, has experienced multiple phases of tectonic evolution since the Cenozoic. During the Early Cenozoic, the Chenghai Fault Zone accommodated part of the eastward extrusion of the Tibetan Plateau through thrust nappe structures. Since the Pliocene, the fault zone has transitioned to transtensional deformation. However, there is ongoing debate regarding the initiation of this transtensional activity and the characteristics of faulting in the southern segment. This study, utilizing remote sensing interpretation, field geological investigations, paleo-tectonic stress field inversion, and focal mechanism solutions, delineates the spatial geometry, activity, and tectonic stress field of the Chenghai Fault Zone's Qina-Binchuan segment since the Pliocene. By integrating previously published geochronological data and seismic records, a tectonic evolution model of the Chenghai Fault Zone since the Pliocene is proposed. The results reveal a migration of fault activity within the southern segment of the Chenghai Fault Zone. The Qingshui-Zhoucheng Fault in the southwestern area exhibited significant activity before the Middle Pleistocene, but its activity has markedly decreased since the Late Pleistocene. Currently, the Bincuan Fault in the southeastern sector shows the highest level of activity, indicating an eastward migration of faulting in the southern segment. Analysis of the fault zone's geometry and stress field inversion suggests that the Chenghai Fault Zone has undergone rotational deformation since the Pliocene. Considering the regional tectonic context, this rotation is interpreted as a tectonic response to the clockwise rotation of the Dali Rift System. This study provides crucial insights into the migration of fault activity during the evolution of strike-slip fault systems and enhances the understanding of the mechanisms by which microblock rotation accommodates deformation during the extrusion of plateau material.
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Meso-Cenozoic tectonic evolution and geomorphologic restoration of the west section of Bonan low uplift, Bohai Bay Basin

Wu Zihan, Hu Zhiwei, Shi Panpan, Dai Liming, Li Sanzhong, Li Fakun, Wang Zhuo, Hu Zihao

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The west section of Bonan low uplift in the Bohai Bay Basin has been found to have great characteristics of medium-deep buried-hill type oil and gas trap in recent exploration work, and internally discovered the Bozhong 26-6 large-scale oil and gas reservoir. Discussions on the formation and evolution of buried-hills, the development sedimentary systems, and the mechanisms of oil and gas generation, storage and migration often require tectonic analysis and tectonic geomorphological restoration work. Therefore, to reveal the complete tectonic deformation and geomorphic evolution of the west section of Bonan low uplift, and to provide theoretical support for oil and gas exploration, this paper, based on the reflection seismic and drilling data in the study area, detailed the strata distribution and tectonic deformation characteristics during Mesozoic-Cenozoic, and used Move software to conduct two and three dimensional tectonic restoration, accurately restoring the geomorphological features during the major periods of tectonic activity. Results reveal that: (1) During the early Mesozoic (from the Indosinian to the early Yanshanian), under the strong compressional orogeny transitioning from a near S-N to NE direction, the study area developed a numerous near E-W and NE directed thrusts, as well as several near S-N strike slip faults. The region experienced intensive uplift, with the overall lack of the Jurassic sedimentation and extensive erosion of the Paleozoic strata. The Precambrian basement was exposed and flattened, presenting a large-scale flattened mountain landform. (2) During the late Mesozoic (from middle to late Yanshanian), under a strong NW-SE directed extensional environment, the reverse faults in the Huanghekou Depression on the south side of the uplift experienced intense negative inversion activity. This allowed the depression to receive a large amount of Cretaceous volcaniclastic and muddy-sandy sediments. The west section of Bonan low uplift and part of the Bozhong Depression on the north side still exhibit uplifted landforms and serve as sediment source areas. (3) During the early Cenozoic (from early to middle Himalayan), under the strong NW-SE directed extensional and rift environment, the study area experienced near S-N directed bidirectional detachment activity. The Huanghekou Depression continued to experience southward faulting, forming a basket-shaped and half-graben shaped structure. The strata in the Bozhong Depression underwent northward faulting and detachment. The west section of Bonan low uplift was affected by transtensional detachment, presenting a geomorphic feature of “high and narrow in the west, low and wide in the east”, ultimately forming the current tectonic pattern of “two depressions with one uplift”, providing space for the deposition of Cenozoic Shahejie Formation source rocks and Dongying Formation cap rocks.
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Zirconium resources and mineralization in China

CHEN Binghan, YU Jinjie, YAO Fojun

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This article divides China's zirconium deposits into alkaline granite type, alkaline complex type, pegmatite type, weathering crust residual slope deposit type, coastal sedimentary type, and river alluvial type. The predicted types of zirconium deposits are divided into the granite type, pegmatite type, coastal sedimentary type, river alluvial type, weathered crust and residual slope deposit type. China's zirconium ore resources are distributed in 15 provinces (autonomous regions) including Inner Mongolia, Hainan, Sichuan, and Guangdong, with zirconium ore reserves in these four provinces (autonomous regions) accounting for 93.7% of the national total. Based on the statistics, the metallogenic period of zirconium deposits in China is divided into Neoproterozoic, Late Paleozoic, Mesozoic, and Cenozoic. 14 zirconium metallogenic belts are divided. 34 Zirconium-related metallogenic series are determined and the metallogenic pedigree of zirconium deposits in China is established. The coastal sedimentary and river alluvial zirconium deposits along the southeast coast can be used as prospects for zirconium exploration.
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The 3D Geological model of Daqiao super-large gold deposit in West Qinling and its ore-forming factors

HE Jinzhong, ZHANG Zhongping, HE Gandi, NIU Pengfei, ZHU Yongxin

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The orebodies of Daqiao gold deposit in West Qinling are characterized by their large-sized scale. In this paper, the 3D model of the ore deposit is used to objectively draw out the spatial structure of gold orebodies and their relation with geological structure of the deposit, and to extract ore-forming factors. The 3D modeling of geological structure of the ore deposit was carried out by using of the geological factors such as gold orebody, special lithology layer, structure and discontinuities, and the 3D models were analyzed. The results are as follows: The matching coefficient between granodiorite dyke and gold mineralization is higher in time than that in space. The marble and part of carbonaceous rocks were related to deep heat flows in the main hydrothermal ore period. The strike-slip faults cut in bevel the fold of bedding fault, of which the axial trace had deflected northward, and they made up a thrust-strike slip tectonic system togather. The main ore-controlling structures are bending of anticline, gently dipping bedding fault, and strike-slip fault. The early hydrothermal ore period of mineralization was controlled by bending of anticline and gently dipping bedding fault, and the main hydrothermal ore period of mineralization constrained by strike-slip fault. The key ore-prospecting indicators are characterized by the silicified rocks covering gold orebodies, and around which there distribute granodiorite dykes, quartz dykes, calcite dykes, calcitized breccia, marble, and carbonaceous rocks. By comprehensive analysis, the key ore factors of the super-large gold deposit, based on ore-forming conditions and ore-forming process in the hydrothermal ore period, can be stated as follows: Products of magmatic hydrothermal mineralization in thrust tectonic system in the early hydrothermal ore period, strike-slip tectonic system, deep magmatic fluid, and large scale of wallrock alternations around the silicified rocks.
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Mineralogical and geochemical characteristics and enrichment mecha-nisms of critical elements in the No. 3 coal seam of the Shanxi Formation in the Hengcheng mining area, Ningdong coalfield

GUO Yajie, SHI Yutao, JI Xiaoyan, MA Shaodong, HUANG Pengcheng, YANG Dequan, CAO Yongbin, SUN Jia, ZHANG Qi, LI Baoqing

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The study of coal-related critical elements deposits has become a frontier hotspot in coal geology research and an important source for increasing reserves of critical elements mineral resources. This study focuses on the No. 3 coal seam of the Early Permian Shanxi Formation at the Maliantai Coal Mine in the Hengcheng mining area of the Ningdong coalfield. It investigates the mineral composition and geochemistry to determine the distribution, occurrence, and en-richment characteristics of elements minerals in the coal, as well as to evaluate their compre-hensive utilization. The study results show that:（1）The No. 3 coal seam at Maliantai is characterized by medium ash yield, high volatile yield, ultra-low total moisture content, and low to medium total sulfur content, with minerals in the coal mainly composed of kaolinite；（2）The major elements in the coal are primarily composed of SiO2 and Al2O3, with minor amounts of Fe2O3, CaO, and MgO. Compared to the average coal worldwide, Li and Zr reach enrichment levels, while Ga, Nb, Hf, Ta, Pb, Th, and rare earth elements (REE+Y) are slightly enriched；（3）Li and Ga are mainly found in kaolinite, Zr (Hf) and Nb (Ta) are primarily found in zircon, and REY is primarily hosted in kaolinite and aluminum phosphate (goyazite) associated with kao-linite. The Yinshan ancient land in the northeast of Ningdong coal field provides important felsic clastic material for the Malitai No. 3 coal, in addition, the Alashan block also provides some volcanic clastic material. The enrichment of critical metals such as Li, Zr (Hf), and Nb (Ta) in the coal is mainly controlled by the input of alkaline-peralkaline felsic clastic materials, with chemical weathering and water-rock interactions being secondary controlling factors. The en-richment of Ga is primarily controlled by the intensity of chemical weathering. The enrichment of REY is mainly influenced by the input of clastic materials and water-rock interaction processes. In addition, the kaolinite content also plays a role in the enrichment of Li, Ga, and REY. Malian Tai No. 3 coal has potential as a source of Li-Ga-Zr-REY metals.
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Time limit of Mesozoic and Cenozoic uplift in the eastern margin of Yinchuan graben：evidence from fission track

Wang ShiZhe, Zhao HongGe, Liu ChiYang, Zhang YiCheng, Wang JianQiang, Wang Jian, Ma Biao, Li Xingcheng

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The eastern margin of Yinchuan Graben is located in the northern part of the structural belt on the western margin of Ordos Basin, at the junction of Alashan Block, Ordos Block and Qinqi Fold Belt with strong activity. The Mesozoic and Cenozoic have experienced multi-stage structural activities, and its structural uplift is of great significance to the study of structural evolution and oil and gas exploration in the surrounding areas. Based on the age, length characteristics and thermal history simulation analysis of apatite and zircon fission tracks in different areas and horizons in the eastern margin of Yinchuan Graben, combined with structural characteristics and stratigraphic contact relationship, this paper points out that the study area has experienced at least Late Jurassic (160~145Ma), Late Cretaceous (100~70Ma), Early Miocene (22~20Ma) and Late Miocene (10~8Ma). There are some differences in uplift characteristics in different periods and regions. The uplift in the northern and southern parts of Mesozoic started earlier (early/middle Jurassic), and it gradually uplifted from the north and south parts to the middle part. The uplift rate in the middle part of late Jurassic was higher than that in the north and south parts, and the whole uplift was slow in the late Cretaceous. Since Miocene, the uplift has been characterized by early south and late north, and the uplift rate increased northward. This uplift period and differential uplift characteristics have corresponding geological response and regional dynamic mechanism.
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Genesis of albitite in the Jiling Na-metasomatism Uraniumdeposit of the Longshoushan Uranium metallogenetic Belt:

Ma Xunjiao, Wang Kaixing, OuYang Hegen, Wang Wei, Yu Chida, Wang gang, Liu Xiaodong

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The Jiling uranium deposit epitomizes a Na-metasomatic uranium deposit in China. However, the formation mechanism of its host albitite has been controversial, limiting our understanding of the ore-forming mechanisms of Nametasomatic-type uranium deposits. Apatite is a common mineral in magmatic-hydrothermal deposits and serves as an essential carrier for tracing fluid sources. In this study, electron probe microanalysis, and LA-ICP-MS isotope and trace element analyses were conducted on apatite from the albitite of the Jiling uranium deposit. Comparative analyses were also made with apatite from the granitic rocks (quartz monzonite, granodiorite, and granite) within the region. The results indicate: (1) The syenite of the Jiling deposit formed during the Late Silurian (429 ± 19 Ma and 429 ± 16 Ma), which is close to the formation ages of the granitic rocks (441~435 Ma) and syenite (428 Ma) in the region; (2) Compared to the magmatic apatite in the regional granites, the apatite in the Jiling albitite shows significantly elevated contents of Cl, Sr, Y, Th, and U, along with decreased contents of F and Fe, as well as a lower F/Cl ratio; (3) The apatite in the Jiling albitite displays similar light rare earth element contents and Sr/Y ratios as those in the apatite of the syenite. These findings suggest that the albitite of the Jiling uranium deposit originates from a hydrothermal system. The sodium metasomatic fluids (including high-temperature uranium mineralization material) originated from the crystallization differentiation of contemporaneous syenites in the region, falling within the magmatic-hydrothermal fluid category. Therefore, in the tectonic zone intersecting the main granite and the northern syenite, favorable conditions exist for the high-temperature uranium mineralization process of the Jiling uranium deposit.
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Application and effectivity of " Satellite-UAV- Spectroscopy" remote sensing three-dimensional survey technology in Li-Be pegmatite ore survey in Altun Mountain,Xinjiang

YaoFojun

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The Altun metallogenic belt is an important lithium metallogenic belt, and in recent years, 9 Li-Be deposits above medium size and 11 Li-Be mine sites have been discovered in Washixia South, Tugman, Tamuqie. Two rare metal metallogenic sub-belts in the south and north have been defined, which has good prospect for finding minerals; however, the working conditions of this belt are harsh, and the degree of geological work is low. it has the importance of the area of great breakthroughs in the search for Li-Be mines. This paper adopts the "Satellite-UAV- Spectroscopy" remote sensing three-dimensional survey methodology and technology, co-operating with ground infrared spectrometer, unmanned aerial vehicle (UAV) hyperspectral and satellite remote sensing technology, sampling multi-spectral remote sensing to identify the rock body and stratum on a small scale of 1:200000-1:50000, and superimposed geochemistry to carry out the selection of Li-Be prospecting area; In the prospecing area, high-resolution remote sensing images are sampled to identify pegmatite veins on the scale of 1:10,000 to define the target area for mineral exploration; and UAV hyperspectral data is used to differentiate the Li-Be-bearing pegmatites on the scale of 1:5000 to achieve rapid and efficient positioning of Li-Be pegmatite veins. This paper shows that the " Satellite-UAV- Spectroscopy" remote sensing three-dimensional survey method is very suitable for the ore-bearing pegmatite veins in Altun Mountain by comparing with the measured ore-bearing pegmatite veins in the field. The problem of integrating "map" with "spectrum" in large-scale mineral mapping is solved and the precise positioning of Li-Be-bearing pegmatites is achieved.
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Genetic relationship of the deposit in Qibaoshan ore-concentration area of Wulian County, Southern Margin of Jiaolai Basin: Constraints of in-situ sulfur isotope and trace element of sulfides

Tang Mingying, Ding Zhengjiang, Zhan Honglei, Zhu Wei, Wang Xin, Wei T, Li Fuhua, Chen Jian, Zou Zhanchun

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The Au-Cu polymetallic deposits represented by the Qibaoshan ore-concentration area of Wulian county is developed in the Southern Margin of Jiaolai Basin, three typical deposits are developed, namely, Jinxiantou Au-Cu deposit, Diaoyutai pyrite deposit and Qibaoshan Pb-Zn polymetallic deposit. In order to further elucidate the genetic relationship between ore deposits, improve the study of ore-forming system in ore concentration area, and establish the ore-forming model of ore deposits, the main sulfides in the ore deposit were tested and analyzed in situ for sulfur isotopes and trace elements of pyrite.. The sulfides in the Qibaoshan ore concentration area has a relatively concentrated sulfur isotope peak distribution range (0‰ ~ 6‰), which comes from the same or similar deep magmatic system.. The Cu, Zn, As, Se, Ag, Sb, Pb and Bi in pyrite show relatively regular changes from Jinxiantou Au-Cu deposit to Diaoyutai pyrite and then to Qibaoshan Ag-Pb-Zn polymetallic deposit, The distribution characteristics of elements show that the ore-forming fluid as a whole presents an evolution process from magmatic hydrothermal to mixed hydrothermal. Comprehensive analysis shows that the deposits in Qibaoshan ore collection area are closely related in time and space. The deposits are the products of the same geological and tectonic environment and different parts of rock construction, which together constitute the porphyry-epithermal Au-Cu-Pb-Zn-Ag polymetallic metallogenic system in Qibaoshan area.
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Sedimentary characteristics and filling model of the PermianFengcheng Formation in Mahu Area, Junggar Basin, NW China

p FontSize=''.''>SUN Jing, ZHENG Menglin, YOU Xincai, ZOU Zhiwen, HE Wenjun, CHANG Qiusheng

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In order to clarify the sedimentary characteristics, distribution laws and filling patterns of all types of reservoirs in the Permian Fengcheng Formation in Mahu area of the Junggar Basin under the theory of the whole oil and gas system, the sedimentary facies types, basic characteristics, distribution laws, evolution characteristics and filling patterns of all types of reservoirs were systematically studied by using data such as logging, coring and 3D seismic of nearly 50 key wells. The results show that the Fengcheng Formation is a fan delta-lake sedimentary system, with fan delta facies mainly developing subfacies such as plain, inner front, and outer front, and lake facies mainly consisting of shoreline shallow and semi deep lake subfacies. The complete sequence and all types of reservoirs, including various types of coarse-grained conglomerates, medium grained sandstones, fine-grained siltstones, mudstones, and alkaline minerals, are developed. Different subfacies and microfacies develop different types of reservoirs. Different periods of fan delta overlap with each other, forming four fan delta groups in the north, west, south, and east of Mahu Area, mainly composed of distributary channel conglomerate and sandstone sediments, with a gradually expanding distribution range. The western block is mainly composed of contiguous wide and long axis fan deltas, while the eastern is mainly composed of isolated narrow and short axis fan deltas. Under the control of four main factors, It has formed three types of fan deltas under water ingress: retrogressive, composite, and progradational.Three types of mixed sedimentary filling patterns, including under , balanced, and over compensation, have developed together. The systematic study of the sedimentary characteristics and filling patterns provides a basis for deepening the analysis of all types of reservoirs and exploration and development in the field of all oil and gas systems.
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Evolution and genetic mechanism of high pressure in the Qianfoya Formation shale gas in the Puguang East syncline in northeastern Sichuan

zhaoniubin, lilingxi, wantao, wanggonghuai, jinda, houxianbo, zhanghao

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In the shale gas reservoir of the Qianfoya Formation in the east-west syncline of Puguang in northeastern Sichuan, overpressure is prevalent.The distribution range, genetic mechanism, and pressure evolution process of the overpressure storage box have not been fully clarified. Based on geological data and logging data, the paper comprehensively analyzes the distribution range, genetic mechanism, and pressure evolution process of the pressure storage box in the first section of Qianfoya Formation shale gas reservoir using the Eaton method, Bowers method, fluid inclusion technology, and basin simulation technology. The results show that: ① The upper floor of the first section of Qianfoya Formation shale gas reservoir is composed of the Daanzhai Member and the bottom of the first section of Qianfoya Formation, consisting of sandy tuffaceous sedimentary tuff, tuffaceous anisotropic quartz sandstone, tuffaceous siltstone, and mudstone. The roof was mainly composed of mudstone interbedded with tight sandstone in the ④ and ⑤ sub-layers of the first section of Qianfoya Formation. Good roof, floor and lateral partition layers avoid the loss of natural gas; ② The overpressure source was mainly caused by fluid expansion due to hydrocarbon generation, followed by structural compression, with a weak relationship with uneven compaction; ③ The abnormal pressure storage box has undergone a stage of organic matter immature-low mature normal pressure, organic matter mature liquid hydrocarbon overpressure stage, organic matter high mature-overmature shale gas abnormal pressure stage, late-stage extrusion and pressure increase and uplift pressure relief collaborative transformation and finalization stage.
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LA-ICP-MS zircon and tantalum-niobium U-Pb geochronology of the Jiabusi Ta-Nb deposit, Daxing'an Mountain

丁, Zhang Yong, Ye Huishou, Yu Jinjie, Fu Xuerui, Wu Shenghua, zhang Tong

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Abstract：The Jibusi Ta-Nb rare metal deposit, accompanied by Li-Rb-Cs mineralization, is a medium-sized Ta-deposit located in the southwest of the Daxinganling rare metal metalization belt. In this paper, through systematic petrographic analysis, rock geochemical analysis and LA-ICP-MS U-Pb chronology analysis of tantalum-niobium, the diagenesis and metallogenic mechanism of the deposit and ore-forming rock were studied. The lithology of ore-forming granite in Jiabusi deposit is mainly jadeite-lithium muscovite-alkalic feldspar granite and lithium muscovite-albite granite. The geochemical data of ore-forming rock shows that their major elements are rich in silicom,aluminum and alkali, but poor in iron, magnesium and calcium, very poor in titanium and phosphorus, which belongs to the peraluminous high potassium calcium alkaline series. Their trace elements are rich in Rb, Th, Nd and Zr, poor in Ba, Nb, Sr and P, strong depleted in Ti. Their rare earth elements (REEs) show very lower ∑REE with average value is 47.97×10-6, have strong negative Eu anomaly and significant M-type “tetradeffect ”. The Zr/Hf of ore-forming granites are between 2.58~3.47，Nb/Ta are between 0.3~0.39, which indicate its belong to Ultra (or extremely) fractionated granite. The ore minerals in Jiabusi deposit are microlite, manganotantalite and Li-muscovite, with Rb and Cs are mainly present in minerals such as lithium mica and tantalum niobium in a similar texture. This paper reports the U-Pb dating results of different granites in the deposit by using LA-ICP-MS method. Zircon U-Pb age of ore-free biotite (hornblende) granite was 144.0±1.0 Ma (2σ, n=16, MSWD=1.3), which represents the diagenetic age of the surrounding rock Narenwula intrusive body. The weighted average age of 206Pb/238U of magmatic tantalum-niobium minerals in mineralized alkalic feldspar granite was obtained at 120.7 ± 0.2 Ma (2σ, n=17/18, MSWD=6). It shows the mineralization age and the diagenetic age of the Jiabusi ore-forming granite intrusion are late phase of Early Cretaceous, which are related to the lithospheric extension after the closure of the Mongolian-Okhotsk Ocean in the Middle Jurassic. The author indicated that the formation of Jabusi deposit can be divided into two stages. The first stage is the primary crystallization stage of magma, which is dominated by Ta and Nb mineralization. The second stage is the self metasomatism stage of hydrothermal fluids, which is dominated by li, Rb and Cs mineralization. Around the Narenwula intrusive rock foundation, there still has the potential of finding rare metal deposits as the same type.
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Tectonic activity history and its dynamic mechanism of the Binhai fault, Hainan Island: New evidences from apatite and zircon fission track analyses

LIN Di, ZHENG Yong, HU Zailong, WEI Changxin, YUAN Qinmin, JIANG Yuhao

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Hainan Island is the largest continental marginal island in the northwestern South China Sea, which is surrounded by Cenozoic rift basins such as Qiongdongnan Basin, Yinggehai Basin, and Beibu Gulf Basin. Thus, it constitutes the major footwall of the boundary fault of these basins. Therefore, the uplift and exhumation history of the Hainan Island contains important information on basin-range coupling process and oil, ores preservation conditions. This study first reports the analyses results of apatite and zircon fission track along the Binhai fault which is the only basin-controlling fault extends into the Hainan Island. The apatite fission track ages range from 23 Ma to 40 Ma, and the average confinement track length ranges in 12.2?13.2 μm, which is relatively small. The zircon fission track ages range from 63 Ma to 82 Ma, and the single grain ages are mainly concentrated in the age groups of 82?78 Ma and 72?69 Ma, respectively. The cooling history of Hainan Island since the Late Cretaceous is generally divided into three episodes. From the Late Cretaceous to the Early Paleocene (82~63 Ma), the whole Hainan Island uplifted rapidly with a total exhumation amount of 3.33 km. During this period, the Hainan Island was jointly affected by the NW compression caused by the subduction of the Pacific plate and the expansion of the middle ridge of the ancient South China Sea, and the Baolun gold mine along the western margin of the Baisha basin was also influenced by the large-scale compressional deformation. From Early Paleocene to Middle Miocene (63?13 Ma), the samples experienced a protracted period of slow cooling, except the western side of the Binhai fault, where also records a rapid cooling from the Middle Eocene to Late Oligocene (40?24 Ma). We attributed this rapid cooling period to the drag effect caused by the accelerated subduction of the Paleo-South China Sea, and the differential uplift on both sides could be attributed to the reactivation of the Binhai fault. During this period, the coarse clasts exhumed from the Hainan Island constitute the key reservoir of the Cenozoic basin. Since the Middle Miocene (13~0 Ma), the exhumation amount is 1.93 km. The compression stress caused by the NNW wedge of the Philippine Sea plate and the long-distance effect of the India-Eurasia plate collision has caused Hainan Island to undergo strong rapid compression and exhumation during this period.
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A comparison of the characteristics of Indosinian and Yanshanian granites and their control on the different W-Sn mineralization potential in Xitian Region, Eastern Hunan Province

Guo Feng, Lu Youyue, Fu Jianming, Guo Jungang, Zhang Fei, Cheng Shunbo, Zhang Zunzun, Zhang Shunxin, Anbang, Zhang Zhongyu

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There are multiperiodic magmation and W-Sn mineralization in Xitian region, Eastern Hunan province, The Indosinian granite mineralization was relatively weak, while the Yanshanian granite mineralization was pronounced. The critical factors controlling the difference in the potential of W-Sn mineralization between the two periods of granite are still unclear. In this paper, we report Zircon U-Pb chronology, Zircon Lu-Hf isotope data, whole rock geochemistry and mineral composition for Indosinian and Yanshanian granites in Xitian region. The zircon LA-ICP-MS U-Pb dating yielded magmatic crystallization ages of 240.0±1.3Ma and 152.9±1.0Ma, corresponding to the Indosinian and Yanshanian periods, respectively. Both periods of granite are characterized by high Al2O3 contents, low MgO contents, enriched in Rb, K, U, Th and depleted in Ti, P, Sr, Ba, Nb. The Zircon εHf(t) values (concentrated between -7.0 and -5.0) and melting temperature(>750℃) of the two periods of granite are similar, The Zircon TDM2 values of Indosinian granite and Yanshanian granite are concentrated at 1.65-1.70Ga, 1.55-1.60Ga, suggesting a magmatic source which was partial melting of ancient crust of the Paleoproterozoic era at high temperature, but the source rocks of the Yanshanian granites are younger than Indosinian granites. The whole-rock Zr/Hf ratios of Indosinian and Yanshanian granite are 26.1-36.3 and 7.0-22.7, and the Nb/Ta ratios are 3.9-7.6 and 1.2-3.9, suggesting that both of them have experienced high differentiation evolution. The magma oxygen fugacity of the Indosinian granite (ΔFMQ=-0.42~2.61) is higher than that of the Yanshanian granite (ΔFMQ=-2.33~-0.08). The Ⅳ(F) of biotite indicates that Indosinian granites have lower concentration of F (Ⅳ(F)=1.15~1.26) than Yanshanian granites (Ⅳ(F)=0.71~0.87). Consequently, more enriched magmatic source region, lower oxygen fugacity and higher F abundance may be the main reasons why Yanshanian granites have more pronounced mineralization than Indosinian granites.
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Spatial and temporal distribution characteristics of Indosinian unconformity in Mianzhu area in the piedmont zone of Middle Longmen Mountains

zhengna

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Due to the complexity of its geological structure and geological evolution, Longmen Mountain has always been the focus of research. The middle part of Longmen Mountains, which has large topographic gradient changes and the most complex magmatic metamorphism, has become one of the ideal areas to reveal the geological structure of Longmen Mountains. At present, there is no unified understanding of several stages of structural activities in the middle part of Longmen Mountains during the Indosinian period. In this paper, we make full use of drilling and seismic data and joint well and seismic demarcation to identify and classify the Indosinian unconformity in Mianzhu area in the piedmont zone of middle section of Longmen Mountains. According to the plane projection of the cut overlap points of the unconformity, we outline the distribution range of various types of unconformity in different periods, construct the chronostratigraphic framework in Mianzhu area, and establish the unconformity evolution model map. The results show that there are four consecutive stratigraphic faults in the early Indosinian stage, 5Myr in the middle Indosinian stage I, 5Myr in the Middle Indosinian stage II, and 28Myr in the late Indosinian stage. Four sets of unconformity were identified from the bottom up during the Indosinian period in the study area: unconformity between Leikoupo Formation and Majantang Formation, unconformity between Xiaotangzi Formation and Member 2 of Xujiahe Formation, unconformity between Member 3 and Member 4 of Xujiahe Formation, unconformity between Member 5 of Xujiahe Formation and Baitianba Formation. In general, the unconformity spread from NE to SW along the Indosinian ancient nappe, which was wide in NE and narrow in SW. From NW to SE, the unconformity changed from angle unconformity to parallel unconformity. The middle part of Longmen Mountains is characterized by multi-stage evolution and progressive deformation from north to south, among which the early and late Indosinian phases are the key structural changes affecting Longmen Mountains to Sichuan Basin. The determination of the spatial and temporal distribution of the Indosinian unconformity in the piedmont zone of middle part of Longmen Mountain and the establishment of the chronostratigraphic framework provide reference for the quantitative study of the Indosinian tectonic belt of Longmen Mountain, and provide a basis for the order of the Indosinian tectonic activity.
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Structural characteristics and growth evolution of the No.8 strike-slip fault zone in Gaoshiti-Moxi area in the central Sichuan Basin

LU Guo, HE Dengfa, TIAN Fanglei, ZHANG Weikang, MA Jia, ZHAO Xiaohui, LIU Huan, LUO Wei

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The intra-craton strike-slip fault system in the central Sichuan Basin, developed above the Neoproterozoic rift system, plays a key role in controlling hydrocarbon migration, accumulation and differential enrichment. In order to deepen the understanding of the structural geometry and kinematic characteristics of the strike-slip fault in the central Sichuan Basin, this paper describes the structural geometry characteristics of the No.8 strike-slip fault zone in the Gaoshitai-Moxi area in detail based on high-precision three-dimensional seismic data, and establishes a three-dimensional structural model of the fault zone. Combined with aeromagnetic data, the relationship between strike-slip fault system and deep rift system in central Sichuan Basin is analyzed. The growth pattern and evolution process of strike-slip fault zone are recovered by fault throw statistics and structural stripping inversion. The study indicates that: 1.The strike length of No.8 strike-slip fault zone is about 70km, and it experiences the variation of NWW-NE-NWW-NE from west to east, causing the right-lateral faulting on the platform of the second and fourth members of the Dengying Formation. The fault zone has typical strike-slip structure styles such as high steep linear structure, "Y" shape structure and negative flower-like structure in the section, and has obvious segmented characteristics in the plane, consisting of 5 main faults, mainly developed horsetail structure and linear structure. 2.The deep Neoproterozoic rift system in the central Sichuan Basin has a good positioning effect on the Sinian-Lower Triassic strike-slip fault system, and the former is the foundation of the latter. The No.8 strike-slip fault zone is controlled by the deep Gaoshitai-Moxi Neoproterozoic rift fault, and the two are "hard connected". 3.No.8 strike-slip fault zone experienced three stages of inherited tectonic superposition on the basis of fault control of deep rift system: initial development stage from Late Sinian to Early Cambrian, growth setting stage before denudation from Late Ordovician to Caledonian erosion, and partial resurrection stage of Early Triassic. 4.There are two growth modes: 1)the fault grows upward from the weak zone of the basement, and the fault throw between the upper and lower strata is the same or gradually decreases. 2)The fault ruptures first from the top, gradually expands downward during the active period, and penetrates with the existing deep weak zone. The fault throw is large on the top and small on the bottom. In summary, The fault zone has experienced the complex deformation of "extension and right strike-slip", which belongs to the multi-stage development and multi-stage link tension-torsion (strike-slip) fault caused by the activation of the pre-existing fault.
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Sedimentary response to glaciation evolution in the Ranwu Lake area, southeastern Tibet since ca. 33 ka

LI Jing, LU Haijian, LIANG Xiao, LI Haibin, PAN Jiawei, LIU Dongliang, ZHAO Zhongbao, CHEN Huan

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Southeastern Tibet is characterized by widespread glacial geomorphology, thus reflecting the dominating role of glaciation in the formation of geological process. However, it remains still unclear with regard to how the sediments respond continuously to the late Quaternary glaciation in this area. A continuous late Pleistocene sedimentary sequence, well exposed at the Ranwu lake area, includes stratified slope deposits, channel deposits, moraine deposits, and loess deposits from bottom to top. Here we firstly analyzed the sedimentary characteristics of this section using sedimentology, paleocurrent data, and conglomerate clast count. Secondly, we obtained the ages of this section through optically stimulated luminescence (OSL) dating. Lastly, we discussed the forming mechanisms of these four types of sediments. Preliminary results are as below: 1) Stratified slope deposits are composed of sands and gravels that exhibit a typical rhythmic layering and were formed at about 33 ka. They reflect the alternating cold and warm climate change and likely belong to a periglacial sediment which are mainly dominated by the combined gelifraction and freeze-thaw processes. 2) Channel deposits consist primarily of variably sized gravels with distinct imbrication and were formed at 32.8~25.1 ka. They were likely produced by the large-scale floods from the northeast due to glacial lake outburst floods. 3) Moraine deposits are composed primarily of poorly sorted gravels, sands, and silts and were occurred at 25.1~11.1 ka, indicating that the Ranwu Lake area was dominated by the glacier flow during the Last Glacial Maximum (LGM). 4) Loess deposits are comprised mainly of fine-grained sands and silts and were deposited during the interglacial period (11.1 ka). They are derived from glacial meltwater debris distributed in the valley which were subsequently transported by glacial wind. In brief, the stratified slope deposits and channel deposits from the lower part of this section were both developed during the interglacial of the Last Glacial Period (the weak warm period of late Marine Oxygen Isotope Stage 3, MIS 3a), while the moraine and loess deposits were formed during the LGM and the Younger Dryas (YD), respectively. This late Pleistocene sedimentary sequence in the Ranwu Lake area well reflects the influence of glaciers variations on sedimentation.
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Geochemical characteristics of apatite and hornblende in diorite of the Zhongguan iron deposit in Hebei Province and their records of petrogenesis and mineralization

caochong, caoqing, zhangyanbo, wangling, dongboxiao, Zhang Rongfang

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The skarn-type iron deposit is an important guarantee of iron ore resources in China. It is necessary to study the source, genesis and evolution of physical-chemical conditions of ore-forming magma for understanding formation mechanism of skarn-type iron deposits. In this paper, the BSE images and corresponding major and trace element compositions of the hornblende and apatite in diorite from the Zhongguan iron deposit are conducted. The source of magma, magma mixing and crustal contamination process, as well as the changes of magmatic physical and chemical conditions caused by these processes are identified. Finally, the necessary magmatic conditions for the formation of the Zhongguan skarn iron deposits are proposed. The results show that the ore-forming magma experienced a double magma chamber system. In the deep magma chamber, the hornblende phenocrysts crystallized in the environment of temperature (average 943 °C), pressure (average 315MPa), oxygen fugacity (average ΔNNO + 0.34) and water content (average 5.97 %). In contrast, the hornblende matrix crystallized in the environment of temperature (average 773 °C), pressure (average 89MPa), higher oxygen fugacity (average ΔNNO + 1.5) and Cl content (average 0.15 %), and lower water content (average 4.87 %) in the shallow magma chamber. The changes of Al2O3 content of hornblende, as well as the 87Sr/86Sr（i）values (from 0.7053‰ to 0.7076‰) of apatite indicate that the ore-forming magma is mainly mantle-derived and mixed with a small amount of crust-derived materials. The obvious core-rim structures are shown in the BSE images of apatite, and the core is generally brighter than that of the rim. The cores are mainly enriched in SiO2, MnO, Ga, REEs et al. In contrast, the rims are more enriched in SO3, Na2O and Cl. Besides, the δEu values of the rims are higher than those of the cores. The chemical composition differences between phenocrysts and matrix of hornblende, as well as the core-to-rim compositional variations of apatite indicate that the ore-forming magma has undergone contamination of gypsum rock strata, crustal material mixing and fluid exsolution during the upward emplacement process, resulting in a significant increase in oxygen fugacity of magma, and promoting the enrichment of volatiles and Fe in magma. In summary, gypsum rock contamination or crust-derived magma mixing and hypabyssal emplacement are necessary conditions for the formation of the Zhongguan skarn high-grade iron deposits.
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The out-of-sequence deformation in the Xuefeng intracontinental fold and thrust belt and evolution of continental lacustrine basin

dengbin, Xu Hongyuan, Li Yingqiang, Tu Guoyu, Jiang Lei, Li Zhi, Liu Chongjiang, He Zeliang, Yong Ziquan, Liu Shugen

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The fold-thrust belt foreland basin system is generally controlled by the process of shallow tectonic denudation-sedimentation and its related coupling mechanism, so it has complex three-dimensional tectonic deformation characteristics and evolution process. Under the remote effect of plate collision, out-of-sequence structures were formed in Xuefeng intracontinental fold and thrust belt in Upside Yangtze region. Based on the structural analysis of deep and large fault zones in the study area, fault calcite U-Pb chronology and deep structural interpretation of seismic profiles, the deformation process of Xuefeng intracontinental fold and thrust belt is reviewed: (1) In the Late Triassic to Early Jurassic (200Ma), the intracontinental fold thrust deformation occurred initially, and the Cili-Baojing fault began to move; (2) In the Late Jurassic and Early Cretaceous (120-160Ma), the multi-layer system slip caused the thrust deformation to extend to the Hubei, Chongqing, Hunan and Guizhou regions, and Jianshi-Pengshui fault began to move. (3) In the Late Cretaceous-Early Palaeo-Modern period (71-52Ma), the Enshi-Youyang and Hefeng-Laifeng faults began to move, and further extrusion folding and thrust-deformation occurred. The fault chronology and the deformation stress field in the study area jointly reveal the process of the Xuefeng intracontinental thrust system showing overthrust deformation before the Indochinese period and the back-camel structure deformation during the Yanshan period, which together form the structural characteristics of the foreland thrust belt with low wedge top Angle and wide deformation area in the Yangtze landmass, and control the formation and evolution of the ancient Yangtze continental lake basin in the Upper Yangtze region.
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Study on hydrochemical characteristics and formation of salt resources in lithium basin of Jiezechaka super large salt Lake, Xizang

madianzhe, zhaoyuanyi, zhengmianping, chenwenxi

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Located in Dongru Township, Ritu County, Ngari Prefecture, Tibet, Jieze Chaka Salt Lake has 2.3 million tons of LiCl resources, 1.6 million tons of B2O3 resources, and 9.79 million tons of KCl resources. It is one of the few lithium mines under development in Tibet. It is of great significance and scientific value to study the material source of the salt lake water and its recharge water. This paper systematically analyzes the Gezechaka salt Lake and its recharge water by means of hydrogeochemical methods. A total of 65 samples of lake water, river water and spring water were collected to test their TDS, pH value and main ion composition. The main ion characteristics, control mechanism and source of lake water and recharge water were studied by Chadha hydrochemical diagram, Piper Cationonic triangle diagram and Gibbs diagram. The results show that the chemical type of salt lake water is Na-CO3, the chemical type of river water is Ca-Mg-HCO3, Na-HCO3, and the chemical type of spring water is Na-HCO3. The composition of hydrochemical ions is mainly affected by rock weathering and evaporation-crystallization. Na+ and K+ of river water and spring water are mainly derived from evaporative karst decomposition such as rock salt, and Ca2+ and Mg2+ are mainly derived from the dissolution of silicate rock. Metallogenic materials such as Li, Rb and Cs come from rock weathering and deep water-rock reaction. The annual replenishment of Hebian Spring, Dongru Spring and Qingshui River is 1,601,600 m3, 6,440,900 m3 and 93,616,500 m3, respectively. River water replenishment accounts for 92.09%, and the annual replenishment of Li, Rb and Cs in river water is about 3501.26kg, 176kg and 156.34kg. The annual replenishment of Li, Rb and Cs in spring water is about 6824.18kg, 288.87kg and 691.59kg, which are mainly spring water replenishment, accounting for 66%, 62% and 82% respectively. Chaka mud fields and membrane fields with an area of about 10.40km2. After extraction of lithium and potassium, the concentration of rubidium cesium in the brine gradually enriched, reaching the requirement of separate mining grade of rubidium cesium in Zabye Salt Lake. The water level of Geze Chaka Salt Lake has risen and its area has expanded. In April 2023, the area of Geze Chaka Salt Lake has reached 118.07km2, an increase of 12.69km2 over 1977, which has had a certain impact on the production of the salt lake. It is recommended to continuously monitor the dynamic change of the lake water.
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Exhumation Processes of the Metamorphic Basement of the Taohua Group in the Southern Margin of the North China Craton: Evidence from U-Th/He Thermochronology

Lei Wanshan, Zhang Rui, Li Sanzhong, Zhou Mingli, Wang Ran, Zhang Haidong

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Uplift and exhumation are important mechanisms of crustal thinning. Understanding the exhumation process of metamorphic basements is crucial for comprehending the lithospheric extension and destruction in the southern margin of the North China Craton since the Late Mesozoic. This study investigates the exhumation history of the Taihua Group metamorphic basement in the southern margin of the North China Craton since the Late Cretaceous using zircon and apatite (U-Th)/He thermochronology. Thermochronological analyses of five sample groups from the Taihua Group gneisses reveal that apatite (U-Th)/He ages range from 32.9 to 41.9 Ma and zircon (U-Th)/He ages range from 56.9 to 94.1 Ma. HeFTy modeling indicates that the Taihua Group metamorphic complex has experienced four stages of cooling and exhumation since the Late Cretaceous: (1) Rapid cooling from the Late Cretaceous to Paleocene (94.1-57 Ma), with a cooling rate of approximately 5.58 °C/Ma, an exhumation rate of about 159 m/Ma, and a total exhumation of 3142 m. This phase of rapid cooling was likely a continuation of the lithospheric thinning of the North China Craton caused by the subduction rollback of the Paleo-Pacific Plate; (2) Slow cooling from 57 to 40 Ma, with a cooling rate of around 1.18 °C/Ma, an exhumation rate of about 34 m/Ma, and a total exhumation of 571 m. This period of stable uplift may be due to the reorientation of the subducting Pacific Plate, reducing tectonic stress in eastern China; (3) Accelerated uplift and exhumation from 40 to 30 Ma, with a cooling rate of about 4.5 °C/Ma, an exhumation rate of 129 m/Ma, and a total exhumation of 1286 m. This phase of rapid uplift might result from the aging of the subducting Pacific Plate (as mid-ocean ridges disappeared and the age of oceanic crust entering the subduction zone increased) and the increase in subduction angle; (4) Slow cooling and exhumation from 30 Ma to the present, with a cooling rate of 0.167 °C/Ma, an exhumation rate of about 5 m/Ma, and a total exhumation of 143 m. This stage of tectonic quiescence likely indicates that the southern margin of the North China Craton has moved away from the active subduction zone of the Pacific Plate. The exhumation process of the Taihua Group metamorphic basement indicates that the large-scale lithospheric thinning in the southern margin of the North China Craton during the Late Mesozoic continued into the early Cenozoic. This phase of uplift and exhumation may have been crucial for the exposure of polymetallic mineral deposits in the southern margin of the North China Craton.
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Structural patterns, ages and geodynamics of late Mesozoic multistage deformation of the Ganzhuermiao dome in the central-southern Daxinganling

YANG Qian, SHI Wei, LI Xiaogang, SHI Jinpeng, LIN Mao

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Under the superimposed influence of the Paleo-Pacific tectonic domain to the east and the Mongol-Okhotsk tectonic domain to the north during the Mesozoic, the Daxinganling and its surrounding areas have experienced the Yanshanian intracontinental orogeny and the succeeding large-scale lithospheric extension and thinning event in Eastern China. Conducting in-depth research on the Mesozoic deformation characteristics, ages and genetic mechanisms of the aforementioned region is crucial for elucidating the Mesozoic tectonic regime transformation in East Asia. In this work, a multi-technique approach, including detailed field structural measurement, inversion of paleotectonic stress fields and zircon U-Pb dating, has been performed in the Ganzhuermiao dome in the central-southern Daxinganling. The new results indicate that this dome experienced at least three-phase deformation during the Middle Jurassic-Early Cretaceous: (1) the top-to-the-WSW ductile shearing during the Middle and Late Jurassic (ca. 160 Ma); (2) NNW-SSE contraction during the Late Jurassic to earliest Cretaceous (144-135 Ma) and subsequent (3) NW-SE extension during the middle-late Early Cretaceous (ca. 135-110 Ma). An age-crustal thickness curve, constructed by published the whole-rock (La/Yb)N and Sr/Y ratio data from the late Mesozoic igneous rocks in the central-southern Daxinganling, shows a good correspondence with the above three-phase deformation. It reveals that the regional crust underwent a remarkable thickening from ~41 km to ~66 km during the Late Jurassic to earliest Cretaceous, followed by a rapid thinning to ~45 km at ca. 125 Ma. Combined with the regional tectonic evolution, we propose that the first two stages of deformation represent the effects of the episode A and B of the Yanshanian Movement, respectively. They shared a regional unified contractional setting. The WSW-orientated ductile shearing may reflect an eastward extrusion tectonic model of NE China controlled by the low-angle subduction of the Paleo-Pacific plate beneath East Asia and the closure of the Mongol-Okhosk Ocean. The late NW-SE extension indicates a change of the regional tectonic regime and suggests the peak destruction of the North China Craton, which may result from the roll-back of the Paleo-Pacific plate and post-orogenic collapse of the Mongol-Okhotsk belt.
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Zircon U-Pb geochronology, geochemistry and Sr-Nd-Hf isotopes of the monzonitic granite in the Yuanpanbei tin polymetallic deposit, Guangdong Province, SE China and its geological significance

Lu Yongyan, Bao congfa, Yan Qinghe, He Xiaohu, Wang He

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Yuanpanbei Pb-Zn-Sn polymetallic deposit, located in Lianhuashan Fault, Eastern Guangdong Province, discovered in recent years, is genetically related to the monzonitic granite. In this paper, zircon U-Pb geochronology, geochemistry, and Lu-Hf isotopes of the monzonitic granite are conducted for the first time. Zircon LA-ICP-MS dating of monzonitic granite yields concordant ages of 151.8±1.5 Ma, which demonstrated that the monzonitic granite is formed in Late Jurassic. Petrographic and geochemical data indicate that monzonitic granite is characterized by weak peraluminous and belongs to the high-K calc-alkaline series, enriched in Rb, Th, U, K, Pb, and depleted in Ba, Sr, Ti, P, Nb, Ta with strong negative anomaly of Eu. Meanwhile，the monzonitic granite shows highly fractionated I-type affinity. The highly fractionated nature, abundant ore-forming metals, low fO2, and close spatial relationship with ore bodies indicate that the monzonitic granite is genetically related to mineralization in this area. The monzonitic granite has relatively high initial Sr isotopes (0.708865 to 0.708918) and relatively low εNd(t) (-6.72 to -7.25) and εHf(t) values (-15.52 to -5.05), with high tDM2 ages of εNd(t) (1568Ma) and εHf(t) (1343~1615 Ma), indicating that the source region of the Yuanpanbei monzonitic granite is most likely from the partial melting of the Mesoproterozoic ancient crustal rocks, which is possibly added by a few mantle material. Based on the results of geochemistry and geochronology, combined with the regional tectonic evolution, the monzonitic granite and tin polymetallic mineralization of the Yuanpanbei deposit were generated in an extensional tectonic setting triggered by the“slab foundering”of Paleo-Pacific plate.
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Nickel and Cobalt metallogenic series andprospecting direction in Qinghai Province

Wang Jinshou, Pan Tong

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Nickel ore is the main part of nickel and cobalt ore in Qinghai, and cobalt is usually produced as associated ores of magmatic nickel ores or contact metasomatic polymetallic ores, and independent cobalt ores are rare. Nickel deposits are relatively concentrated in the Qinling-Qilian-Kunlun metallogenic domain, South Qilian metallogenic belt and East Kunlun metallogenic belt nonferrous metal ore concentration area, the deposit type is magmatic, which is closely related to mafic-ultramafic rocks intruded by mantle-derived magma through deep liquation, and the abnormal enrichment and mineralization mostly occurred in the Early Paleozoic Ordovician (South Qilian metallogenic belt) and Devonian (East Kunlun metallogenic belt). The mineralization was formed in a post-collisional extensional environment during the late evolution of the Proto-Tethys. Cobalt deposits are mainly distributed in Qinling-Qilian-Kunlun metallogenic domain and Tethyan metallogenic domain, but independent cobalt deposits and associated cobalt deposits with economic value are exposed in East Kunlun metallogenic belt, South Qilian metallogenic belt and a"nyemaqen metallogenic belt. The main types of cobalt deposits are magmatic, marine volcanic and contact metasomatic; The metallogenic epoch of cobalt deposits is complex, which can be divided into four metallogenic stages, namely, Ordovician and Silurian of Early Paleozoic, Devonian and Carboniferous of Late Paleozoic and Triassic of Mesozoic. The metallogenic geological environments of different metallogenic stages are significantly different. The metallogenesis varies with the types of deposits, but it is basically consistent with the enrichment and formation process of the main ore species. The mineralization of Ordovician-Devonian is in the extensional environment after orogenesis. Forming magmatic deposits related to mafic-ultramafic rocks of non-ophiolite type; forming marine volcanic rock deposits in the Carboniferous period in the oceanic spreading environment; forming contact metasomatic deposits in the Triassic period related to the magmatic intrusion of continental margin arc. According to the spatial and temporal distribution characteristics, mineralization and metallogenic geological background of the deposits, the nickel and cobalt deposits in Qinghai are divided into 10 metallogenic series, 15 metallogenic subseries and 9 deposit types. Base on that regional metallogenic geological setting, regional metallogenic condition, the known mineralization information and the latest prospecting results, the regional element geochemical field, the metallogenic Serie of ore deposits and the research degree analysis, the prospecting potential of different types of nickel and cobalt deposits in the metallogenic belt is proposed. The South Qilian metallogenic belt, the northern Qaidam metallogenic belt and the East Kunlun metallogenic belt in the time-space domain of the former Tethys Ocean tectonic activity are still the first possible prospecting areas, and the field investigation should focus on the Ni-rich iron series basic-ultrabasic rocks unrelated to ophiolite, and then the magmatic nickel deposits related to ophiolite mafic-ultramafic rocks should be explored in the ophiolitic melange belt. For the less studied cobalt deposits, the first is to focus on the metallogenic geological environment and favorable metallogenic conditions of independent cobalt deposits of marine volcanic rock type, and the second is to focus on the occurrence state and abnormal enrichment mechanism of Co element in known deposits; The northern Kunlun magmatic arc in the Galinge-Yemaquan area in the western part of the East Kunlun metallogenic belt and the Qimantag-Xiariha magmatic arc in the Dulan area in the eastern part of the East Kunlun metallogenic belt are favorable for finding contact metasomatic polymetallic associated cobalt deposits. The East Kunlun metallogenic belt and a"nyemaqen metallogenic belt may become important prospecting areas for marine volcanic cobalt deposits related to the oceanic ridge magmatism during the spreading period of the Paleo-Tethys Ocean. In general, magmatic nickel deposits, marine volcanic type independent cobalt deposits and paragenetic cobalt deposits, magmatic type associated cobalt deposits and contact metasomatic type associated cobalt deposits can be regarded as the main direction of future exploration of nickel-cobalt deposits.
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The Neoarchean structure characteristics and geological significance of the Taishan Group,Western Shandong Province

Li Xiaodong, Wang Wei, Tian Zhonghua, Jia Du, LuoBowen, Zhou Jinwei

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Due to the influence of Paleoproterozoic metamorphism and deformation, the structure characteristics of the Archean basement of the North China Craton were blurred. The central region of the Western Shandong Province, located in the eastern part of the North China Craton, developing 2.7~2.5 Ga supracrustal rocks, are almost not affected by the Paleoproterozoic events. In this study, detailed field structure analysis and geochronological work were carried out. We suggested that the Taishan Group was subjected to three stages of deformations: early foliation(S1) and tight folds(F1) formed in the stage DA-1. Large upright folds, foliation(S2) and thrust faults formed in the stage DA-2. In the stage DA-3, lots of ductile shear zones formed. Combined with some published chronological data, we proposed that the stage DA-1 occurred in >2.56~2.53 Ga, the stage DA-2 occurred in 2.53~2.52 Ga, the stage DA-3 occurred in 2.52~2.50 Ga. Large number of structural geometric features in peak deformation stage indicate that the deformations of the Taishan group is different from those of the dome and keel structure under the vertical mechanism. It is similar to the structure formed by the lateral extrusion orogeny of the Phanerozoic. Accordingly, we suggest that the Archean horizontal structure in Western Shandong is the result of horizontal movement under the plate tectonic system.
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Genesis analysis of the Nanpu Sag, Bohai Bay Basin: Insights from Seismic Data Interpretation and 3D Sandbox analogue Modelling

wangyuheng, yufusheng, songlu, wangdandan, zhaobaoyin, qiyili, menglingjian

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The formation process of rift basins is influenced by multiple factors, including pre-existing structures, sedimentary material properties, rift phases, and directions. Ultimately, this process results in multiple sets of fault systems with different orientations and scales, leading to the formation of various structural styles. This undoubtedly makes the structural analysis of basins highly challenging. In this study, we replicated the evolution process of the Nanpu Sag since the Dongying Formation, which underwent N-S extension under the influence of multiple factors, through the interpretation of 3D seismic data and comparison with analogue modellings of group structures. The study reveals the following findings: The Nanpu Sag is a result of multiple-phase rifting developed under pre-existing structures. Eventually, it formed a structural pattern of N-S partition deformation, connected in segments from east to west, and vertically deformed within the Minghuazhen formation. The pre-existing paleo-uplift in the southern part of the sag affects the uniformly distributed extensional deformation, while in the northern part, a segmented interconnected mesh-like fault system is formed. Reactivation of pre-existing structures in the southern part leads to the formation of E-W curved en echelon inherited fault systems on both sides. The NE pre-existing fault planes formed during multiple-phase orthogonal rifting processes are important factors restricting the late-stage oriented arrangement of faults. Ductile detachment layers are key material factors that enhance the interaction between faults, transmitting strain initiated from the preset boundary to various parts of basin deformation. They facilitate the connection of isolated faults, forming E-W segmented connected normal fault combinations. The faults accommodate oblique extension caused by pre-existing structures through their own bending.
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Nature of the Ore-hosting Sedimentary Rocks of the Orogenic Gold Deposits in the South Tianshan: An example from Awanda Gold Deposit

Yilidanna TALATI, Nijiati ABUDUXUN, LIU Xueliang, Abidan ALIMUJIANG, YANG Gang

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Orogenic gold deposits in the South Tianshan are commonly hosted in meta-sedimentary rocks. The age of formation and nature of these sedimentary rocks remain controversial. By integrating previous investigations on the Awanda gold deposit with our new results of recent studies, we discuss the tectonic nature of the ore-hosting meta-sedimentary rocks. The area contains fragments of Ocean Plate Stratigraphy (OPS) that are mainly composed of pillow basalts, ribbon cherts, and turbidites. Radiolarian micro-fossils are found in 30 samples of the ribbon chert. They are mostly entactinids, which are identified to be Late Devonian to Early Carboniferous in age. The ore-hosting sedimentary rocks in the Awanda gold deposit and the turbidites from the OPS have similar maximum depositional ages, which are consistent with the ages of radiolarians from the ribbon cherts. According to the conceptional model of OPS, integrated with regional geological records, we consider that the meta-sedimentary rocks are main parts of the South Tianshan accretionary complex, and they belong to orogenic non-Smith strata that formed on the leading edge of the southern Yili-Central Tianshan active margin, rather than on the passive margin of the northern Tarim Craton. Faults with various scales and structural levels are well developed in the accretionary complex, which are closely related to gold mineralization in the South Tianshan. “Convergent margin-related meta-turbidites + deformation + magmatic hydrothermal fluids” is proposed to be a key prospecting criterion for orogenic gold mineralization in the South Tianshan.
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Study of the fine-scale sedimentary characteristics in the western margin of the Weihe basin using passive seismic imaging with a dense linear array

Xu Yong, Deng Bao, Tian Xiaofeng, Ni Hongyu, Duan Yonghong, Xiao Benfu, Li Junlun

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In order to investigate the subsurface fine structure and sedimentary characteristics of the key areas with high earthquake risk in the western margin of the Weihe basin, we deployed a dense linear array consisting of 254 short-period three-component seismometers with an average station-spacing of 200 meters in this study, which collected data for 30 days. We calculate the vertical component cross-correlation of the ambient noise, apply the recently developed extended range phase shift method to extract the fundamental mode Rayleigh wave dispersion curves ranging from 3 Hz to 3.3 s, and then invert for high-resolution shear wave velocity structure down to the depth of 2.5 km beneath the dense linear array. Additionally, using the collected three-component seismic noise, we apply the horizontal to vertical spectral ratio (HVSR) method to calculate peak frequencies, and then use an empirical relationship to estimate the thickness of sedimentary layers in the Weihe basin. The tomographic results show horizontal pattern with a high-low-high velocity variation, corresponding to the uplift-depression-uplift geological structure in this sedimentary basin. The result also clearly delineates three major faults and two geological structural units in the region, consistent with the profile obtained by active seismic imaging. The result from HVSR reveals that the sedimentary layers are relatively thick and exhibit a distinct and complete stratigraphic sequence deposited in the Holocene, Neogene, and Quaternary periods in the Cenozoic era. A comprehensive analysis integrating results from ambient noise tomography, HVSR and active-source imaging suggests none of the three major faults beneath the 2D array penetrates through the Quaternary formation in this region. This study shows that the extended range phase shift and the HVSR methods based on seismic ambient noise are effective in characterizing structures in sedimentary basins.
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Characteristics of the fault system in Nanpu sag and its Cenozoic evolution

SHANG Lin, GAO Guangliang, YAO Dandan, SUN Yanchun, WANG Miao, LI Chunlin

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The Nanpu sag is located in the eastern part of the North China Craton and is a hydrocarbon-rich sag in the northern part of the Bohai Bay Basin. There has been a long-standing debate regarding the tectonic evolution model of the Nanpu sag, specifically whether it is formed by extensional faulting superimposed by strike-slip faulting to create a sag or if it is the result of multi-stage extensional faulting forming the sag. This study conducted structural interpretation on eight seismic profiles traversing the Nanpu sag and identified NE–SW-striking fault zones characterized by listric normal faults, domino-style normal faults, X-type normal faults, graben-horst structures, and extensional duplex structures, representing typical extensional deformation systems. The NW–SE-striking fault zones exhibited left-lateral strike-slip and oblique extension features, mainly serving to accommodate southward movement of the hanging wall of NE–SW-striking normal faults. Analysis of structural maps of stratigraphic boundaries during different geological periods in the Nanpu sag revealed a migratory pattern of the sedimentary center in the Cenozoic from NW to SE. Based on the above analysis and incorporating regional tectonic evolution data, this study proposed a four-stage tectonic evolution model for the Cenozoic in the Nanpu sag, suggesting it underwent a multi-stage extensional faulting. This work not only serves the purpose of aiding future oil and gas exploration in the Nanpu sag but also contributes valuable material for theoretical studies on fault systems.
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Pliocene tectonic transformation from strike-slip to thrust along the eastern margin of Pamir

王, WANG Xin

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The structural characteristics and evolution history of the eastern margin of Pamir are of great significance to reveal the deformation and evolution of the western syntaxis of the Tibetan Plateau, the basin-mountain coupling relationship between the Pamir–West Kunlun and the Tarim Basin, and to guide the exploration of oil and gas resources and earthquake disaster prevention in this region. Based on the detailed surface mapping and structural analysis of seismic profiles across key locations, the tectonic framework of the basin-range junction zone in the eastern margin of the Pamir is constrained. The mapping data, field photos, seismic profiles and other data presented in this paper reveal that a dextral strike-slip fault system outcrops in the eastern margin of the Pamir, and a buried compressional thrust belt develops in the adjacent basin, including the Qipan structural wedge and the Qimugen structural wedge. The growth strata of the Qipan structural wedge is located in the lower section of the Pliocene Artux Formation, while the growth strata of the Qimugen structural wedge is located at the top of the Pliocene Artux Formation, indicating that the thrust belt has been developed since the Pliocene. The eastern margin of the Pamir experienced a tectonic transformation from a strike-slip tectonic system to a compressional tectonic system during the Pliocene. Before the Pliocene, deformation was accommodated by dextral strike-slip of the Wuyitake-Momoke transfer system (WMTS); Since the Pliocene, deformation in this area was dominated by eastward thrusting, and the strike-slip activity decreased. These basic data and the basic viewpoints put forward in this paper have a good guiding significance for establishment of the tectonic framework and evolution sequence of this region.
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Multi-stage tectonic events constrained by apatite fission-track thermochronology in the Outang-Chuxian-Shangyaopu, Anhui Province

TIAN Pengfei, He Zifei, Lv Jinliang, He Yajie, YUAN Wanming, YANG Xiaoyong, DUAN Liuan

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The Outang-Chuxian-Shangyaopu area in Anhui is located in the southeastern margin of the North China Craton, the northern margin of the Middle-Lower Yangtze River Ore Belt, the northern frontal belt of the Qinling-Dabie orogenic belt, and the east side of the Tanlu fault zone (TLFZ). The study area is located at the intersection and transition of various large-scale regional dynamical systems, and a large number of copper deposits are developed around it, which has important economic value. However, the degree of low-temperature thermal history research in the region is low, and the analysis of the thermal history of apatite fission track in this region is of great significance for understanding the regional tectonic evolution. We used apatite fission track to study the tectonic activities in the area of Outang-Chuxian-Shangyaopu. In this paper, we obtained nine apatite fission track results with central age between 113.2±7.8 Ma and 78.6±5.3 Ma. The study reveals the TLFZ has experienced multi-phase thermal events. The Outang-Chuxian-Shangyaopu area showed rapid exhumation at 130~100 Ma, possibly related to the high-speed oblique subduction of the Izanagi plate. The exhumation of the study area was relatively slow from ~100 Ma, until ~60 Ma when the far-field effect of the Indian plate and the Eurasian plate was reflected in the Outang-Shangyaopu area. After the hard collision between the Indian plate and the Eurasian plate started, the Outang-Shangyaopu area was exhumated rapidly. Especially, the thermal history clearly reflects the impact of the hard collision between the Indian and Eurasian plates (55~52 Ma) on the thermal history of the study area, and then the study area was controlled by two tectonic systems, which are the subduction of the Pacific plate and the long-range effect of the collision between the Indian plate and the Eurasian plate.
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The genesis and tectonic significance of the Xinchang granites in Beishan, Gansu Province and its implications for the geological disposal of High-Level Radioactive Wastes (HLWs): Constraints from geochemistry, zircon U-Pb chronology and Lu-Hf isotopes

GUI Rengao, WANG Ju, SUN Jia, SHI Kaituo, XIAO Wenzhou, ZHOU Miao, ZHANG Xiaoping, LI Nan, WU Peng, DUAN Xianzhe

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Xinchang, located in the eastern section of the southern part of Beishan, Gansu province, is a key area for studying the tectonic evolution of the southern part of Beishan and evaluating the site selection in the geological disposal of HLWs. The Xinchang granitoids are composed of three lithofacies units: medium-fine biotite monzonitic granite, granodiorite and gneissic tonalite. Biotite monzonitic granite and granodiorite are generally rich in silicon, potassium (K2O>Na2O), and alkali, and have medium aluminum. These two granites belong to weak peraluminous and high potassium calc alkaline A2 type granite. The tonalite is rich in sodium (K2O
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Banded iron formation: Advances and challenges in Cyclostratigraphy

BAI Yang, MA Kunyuan, ZHANG Lianchang, WANG Changle

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Banded iron formation (BIF) is chemical marine sedimentary rock that was exclusive to the Precambrian. They constitute a significant component of early crust and provide valuable insights into the tectonic evolution, ancient environmental changes, and primitive life activities on early Earth. BIF exhibits distinctive rhythmic band at various scales. Despite considerable progress in understanding the sources of ore-forming materials and depositional conditions of BIF, ongoing debate persists regarding the formation of bands at different scales. In recent years, geologists have identified numerous reliable Milankovitch cycles records within BIF stratigraphy, leading to innovative theories proposing astronomical forcing as a driving factor for the formation of diverse rhythmic bands in BIF. This paper presents a comprehensive review on cyclostratigraphy in BIF, with specific focus on exploring the impact of climate change driven by Earth's orbital parameters on BIF. Furthermore, this study presents key unresolved issues and explores future prospects for cyclostratigraphic studies on BIF in the North China Craton.
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The basement dipping’s control on the structural deformation of the Longmenshan thrust belt

Yu Jingqiang, zhao li, Zhang Yunyin, Dong Dawei, Yu Zhengjun, Wang Yongshi, Zhang Pengfei, Wei Wen

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The basement dipping is an important factor controlling the structural deformation of thrust belts. However, rare attentions have been paid on the basement dipping characteristics of the Longmenshan thrust belt. Based on interpretations of seismic profiles, this paper found that the Longmenshan thrust belt in the northern, central and southern segments underwent different basement dipping. The basement dipped 2.6° toward foreland in the northern because of the uplift of thrust sheets. The basement dipped 3.2° toward hinterland in the central due to several phases of loading. The basement dipped 2.6° toward hinterland in the southern which was the result of earlier rifting and later loading. The numerical experiment shows that the basement dipping toward hinterland or horizontal subsiding will suppress the forward propagation of thrusting deformation, and superimposed the thrusting sheets. While the control effect of the pre-existing basement dip is opposite. When the basement remains horizontal or dip toward the foreland, the thrust sheets in hinterland uplifted stronger than that of the foreland, which will cause the basement dipping toward the foreland as a whole. When the basement dipped backward with syn-sedimentation will result in the back-thrusting in slope zone. Numerical simulation proved the basement evolution in southern segment of the Longmenshan thrust belt. Before the Late Cretaceous, it was in an extensional regime with thick strata in the west and thin strata in the east, and its basement dipped to the west. During the Late Cretaceous—Eocene, a foreland basin developed, and the basement dipped toward hinterland because of the loading. During the Oligocene—Miocene, the thrusting deformation strongly propagated into the basin, and the basement almost had no dipping. Since the Pliocene, the basement in hinterland has been uplifted because of the Qinghai-Tibet Plateau, which resulted in the sharp topography.
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Numerical Simulations Reveal the Control of Lithospheric Strength Structure on Passive Continental Margins’ Evolution

Fan Qingkai, Guo Jinrui, Gao Min, Wu Gaokui, Wang Yanyang

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The formation and evolution of passive continental margins are controlled by the pre-rifting lithospheric strength and its vertical structure. In order to investigate the effect of two factors on lithospheric breakup time, faulting styles, sizes and morphology of passive continental margins, we define two comprehensive indexes as integrated lithospheric strength (σe) and crust-mantle rigid layers coupling degree (Coc), and reveal the influences through geodynamic numerical modelling. According to simulations, the strength structure of lithosphere plays a key role in controlling its rifting duration, a stronger pre-rifting lithosphere inevitably causes a longer lasting rifting, and on this basis, the decrease of the Coc will prolong this process further. For the fully coupling lithosphere (Coc=1), upper crust usually breaks first, and will form symmetric margins through a ‘pure-shear’ mode. When Coc decreases, rigid layers of upper crust and upper mantle deforms separately, and an asymmetric continental margin will form by lateral migration of the rift center. Under such circumstances, the upper mantle with a relatively limited thickness will break first, while when a thick upper mantle develops, the upper crust will break first and lead to the exhumation of mantle rocks. In addition, a low Coc is necessary to generate large-scale passive continental margin basins with a broad and gentle geometry, and the lower Coc is, the greater the migration distance of the rift center and the conjugated margins are. Thickening of the crust will lead to the decreasing of Coc, which will also enlarge the scale of continental margins. Those understandings can be verified on the central segment of South Atlantic continental margins.
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Metallogenic regularity and model of Paleogene-Neogene anticlinal fissure pore brine in central and western Qaidam Basin

Han Guang

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In recent years, deep fissure pore brines have been found in Paleogene-Neogene anticlinal tectonic strata in the central and western Qaidam Basin, Qinghai Province. These brines have large reservoir thickness, high content of potassium, lithium and boron resource elements, and some metallogenic conditions have reached the boundary or industrial mining grade, which have great potential for further prospecting. In this study, the sedimentary and salt-forming evolution of Paleogene-Neogene strata, reservoir characteristics and element geochemistry of brine deposits in Qaidam Basin are reviewed in detail, and the spatio-temporal metallogenic characteristics and genetic mechanism of brine resource elements are summarized. The results show that the reservoirs of brines in the west of the basin are gray mudstone and mudstone, while in the central of the basin are mudstone and siltstone. The content of potassium, lithium and boron resources gradually decreases from the west (Shizigou -Nanyishan) to the central (Hongsanhan - Yanhu) and to the north (Eboliang - Lenghu - Nanbaxian), which is closely related to the migration and evolution of the sedimentary center of the ancient lake basin. The metallogenic model of the Paleogene-Neogene anticlinal fissure pore brine deposit is established, which has a good guiding significance for future exploration evaluation and metallogenic prediction.
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Petrogenesis of granites and its relationship with uranium mineralization in the Xiazhuang pluton, northern Guangdong Province: Constraints from zircon trace element and mineral chemistry

TAO Jihua, Zhang Zefeng, Renzhi, XU Zhitian, SUN Junjie, CAO Jun, SU Xianyuan, LENG Chengbiao, XU Deru

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The granite-hosted uranium deposits in South China are spatially associated with the U-rich granites (U﹥10×10-6). Understanting the petrogenesis of these uranium-bearing granites with high U contents is not only significant for formulating exploration strategies for granite-hosted uranium deposits in South China, but also for ta better insights into the mechanism of U enrichment and mineralization for the granite-hosted uranium deposits. Here we investigate the Xiazhuang garnites which represent typical U-bearing granites with high U contents, using zircon U-Pb dating and zircon trace elements, biotite and chlorite geochemistry data, to constrain the petrogenesis and its relationship with uranium mineralization. LA-ICP-MS zircon U-Pb dating shows that the Xiazhuang granites were emplaced 234~236 Ma. The parental magmas of Xiazhuang granites were derived from the partial melting of Paleoproterozoic metasedimentary rocks with high F contents, and then underwent relative highly degree of magma differentiation. The oxygen fugacity decreased and U contents increased with the magmatic evolution, which led to the formation of U-rich granites (U﹥10 ×10-6) containing a large amount of U-rich accessory mineral such as uraninite, monazite, xenotime and thorite. Our study suggests that the U-rich accessory minerals in Xiazhuang granites were altered by the hydrothermal fluids in relatively acidic and oxidizing conditions in response to the Yanshanian mafic magmatism, followed by uranium leaching during alteration and provided uranium sources for the uranium mineralization.
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Geology, geochemistry and of the Chakeng copper-potash feldspar deposit in Dehua district, Fujian province，and a preliminary discussion for its genesis

Zhang Chengjie, Qiu Tian, Xiong Fahui, Wen Wu, Mu Xiaoping, Chen Qin

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The Chakeng copper-potash feldspar deposit (236 t Cu and 41.52 wt potash feldspar), located in the central part of polymetallic mineralization concentrated area of Mesozoic magmatic belt along southeast coast, is hosted in Qiongxi biotite granite in Dehua district, Fujian province. Copper ore bodies and potash feldspar ore bodies are the mainly two kinds of orebody in this deposit, both of which are controlled by a group of NNE trending faults F1, F2 and F3, and their secondary faults. The ore-forming process consists of three stages: potassic metasomatism (I); silicification and muscovite alteration (II) and carbonatization (III). Stage I and II are the major period for potash feldspar and Cu mineralization, respectively. Cu mineralization is strictly superimposed on potash feldspar mineralization, forming Cu- and potash feldspar-rich ores. Based on the geology, mineral chemistry, whole-rock geochemistry and internal structure of zircon, we propose that the Chakeng deposit is a hydrothermal-metasomatic deposit. Magmatic zircons separated from the copper-potash feldspar ore were probably captured/inherited from Qiongxi granite by hydrothermal fluids. Zircon U-Pb dating yielded a concordant age of 159.4±1.0 Ma (MSWD=0.21), which is interpreted as the petrogenic age of Qiongxi granite, and also defined as the upper limit of ore-forming age. Granite porphyry, intruded in biotite granite in Chakeng area, is characterized by enrichment of Ba, Sr, P, Ti, Pb and Cu, which is similar with the copper-potash feldspar ore but much higher than biotite granite. It is inferred that the copper-potash feldspar mineralization possibly resulted from the evolution of granite porphyry in this area.
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Lithology identification of Karamaili ophiolite belt in Xinjiang based on ASTER and SDGSAT-1 thermal infrared data

Liulei, Zhang Zhao, Zhang Qunjia, Mei Jiacheng

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Thermal infrared spectrum (TIR, 7-14 μm) has unparalleled advantages for the identification of rock-forming minerals, but currently there are few available satellite borne thermal infrared data sources, and the spatial and spectral resolution of the images is generally low. The thermal infrared spectrometer (TIS) carried by China's Sustainable Development Scientific Satellite-1 (SDGSAT-1), which will be launched in 2021, is characterized by large bandwidth (300 km), high spatial resolution (30 m), and high detection sensitivity, and has a better application prospect in lithologic mapping. In this study, two kinds of thermal infrared images, ASTER and SDGSAT-1, were selected from the East Junggar Kalamari region of Xinjiang to establish rock indices of mafic–ultramafic rocks, quartz-rich rocks, feldspar-rich rocks, and granitoid rocks, and combined with the results of the principal component analysis to analyze the distribution characteristics of the different rock types in the 2D and 3D feature spaces, and constructed the lithology identification models of the two kinds of data in the multi-dimensional spectral feature space, respectively. The results show that: 1) The rock indices constructed from ASTER TIR and SDGSAT-1 TIS data can effectively identify mafic–ultramafic rocks, quartz-rich rocks, feldspar-rich rocks and granites, with an overall accuracy of 95.16% and 98.02% for lithology identification, respectively; 2) The multi-dimensional spectral feature space model constructed with two types of data also has good lithology recognition performance, with overall accuracy improved to 96.78% and 98.54%, respectively; 3) SDGSAT-1 TIS has improved the accuracy of extracting mafic-ultramafic rocks by 13.26% compared to ASTER TIR, and has stronger recognition ability for rocks with smaller outcrops. It has great potential for application in lithology mapping.
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New insight into the mechanism of No. 1 fault in the Yinggehai Basin: analogue modelling and discussion

Xiao Kunze, Tong Hengmao, Yang Donghui, Li Xuesong, Li Xushen, Cui Hao

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The Yinggehai Basin has long been of great interest to academics and the petroleum industry due to its special tectonic location (the area of the Red River Fracture Zone into the sea) and its abundant natural gas resources. Since the Indo-Eurasian collision-extrusion model was proposed to explain the deformation in Southeast Asia, the Yinggehai Basin has been regarded as a typical pull-apart basin. However, based on the generalised fault theory, and through the structural analysis of the 3D seismic data system, they revealed that the tectonic features and the distribution of fault distances of the boundary fault (No.1 fault) in the Yinggehai Basin are not similar to those of the traditional strike-slip faults, but they are also strongly similar to the features of the structural deformation under oblique extension. Furthermore, our article proposes a new insight into the mechanisms of the No. 1 fault based on the analysis of the structural features of the No. 1 fault and also combined with the analogue modelling. The results show that the No.1 fault has obvious characteristics of an oblique-slip normal fault, and there are significant differences in the amount of strike-slip and dip-slip displacements in different areas along the fault strike, as well as the control of sedimentation in the basin. The boundary fault was an oblique-slip normal fault due to the reactivation of pre-existing structures under a north-south extensional stress regime during the Oligocene-Miocene period, and these r insights were also verified by analogue modelling. A new insight into the mechanism of the No. 1 fault, which theoretically reveals the mechanism of the Yinggehai Basin and can provide guidance for the structural analysis of the Yinggehai Basin and its later oil and gas exploration and development.
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Zircon U-Pb ages and Rubidium occurrence of the giant Gariatong granite-type rubidium deposit, Tibet

XIE Jinling, TANG Juxing, LIN Bin), TANG Pan, QI Jing, DENG Shilin, HE Liang, ZHANG Xiaoxu

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Lots of highly differentiated granites are widely distributed on the Qinghai-Tibet Plateau, but their mineralization and exploration potential for rare metals were unclear. The Gariatong deposit is a newly discovered giant granite-type rubidium deposit in the central Lhasa terrane, recently. The detailed geological survey and borehole logging of the Gariatong deposit revealed that the rubidium mineralization is mainly hosted in monzogranite and surrounding rocks. Zircon U-Pb dating results show that the weighted average ages of the ore-bearing monzonite is 20.0±0.5 Ma (n=14, MSWD=1.8), which suggested that the intrusion occurred in the Miocene. Detailed petrography and electron microprobe analyses revealed that rubidium is mainly host in muscovite and biotite in an isomorphism form, and no independent rubidium minerals are seen. The geochemical characteristics of muscovite and biotite revealed that the magma associated to mineralization is the product of remelting of crustal-derived material in a low-oxygen fugacity environment, and the formation of fluoride-rich magmatic hydrothermal fluids after strong differentiation is the key to the formation of large-scale rubidium mineralization. The discovery of the giant granite-type rubidium deposit in the Gariatong not only enriched distribution of rubidium mineral resources in China, but also support the prospecting of rare metals in highly differentiated granites on the Qinghai-Tibet Plateau.
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Late Triassic extension in the northwest Ordos Basin: Constraints from Langshan basalts, NW China

huijie, fanliyong, zhaoweibo, kangrui, wangyufei, zhangjin, zhangbeihang, zhaoheng

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This study reported newly discovered Triassic basalts in the Langshan region, analyzed its tectonic setting and contemporaneous deformation, and discussed the characteristics of the Late Triassic basin in the northwest margin of Ordos Basin. 40Ar/39Ar geochronology show that the basalts formed in the Late Triassic (217 Ma). Whole-rock geochemistry reveals that the basalts have OIB affinity, derived from the 5–10% partial melting of garnet and spinel lherzolite, formed by the decompression melting of the asthenosphere in the intraplate extensional setting. The Langshan region also developed a Late Triassic NE-SW trending ductile sinistral shear zone, which connected southward with a simultaneous sinistral shear zone in the Bayanwulashan and Helanshan regions and extended northward into Mongolia. Temporal simultaneity indicates the close relationship between sinistral shearing and basalts eruption. By comparing the contemporaneous basalts, Yanchang Formation, and sinistral strike-slip faults in the Langshan and Helanshan regions, we proposed that the northwest margin of the Ordos Basin was under the far-field effects of the collision of North China Plate and South China Plate in the Late Triassic, and the sinistral ductile strike-slip lead to the formation of regional pull-apart basin, accompanying the extension of lithosphere and the basaltic magmas eruption resulted from the decompression of asthenosphere.
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Characteristics of trace element geochemistry and the geological significance of fluorites from the Haidewula uranium deposit in Qinghai

Wu Jia, Liu Xiaodong, Wang Kaixing, Dai Jiawen, Yu Chida, Sun Liqiang, Zhu Kunhe, Yang Jianjun

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The Haidewula uranium deposit is the first typical volcanic-related hydrothermal uranium deposit to be discovered in northwest China currently. Revealing the nature of the ore-forming fluids and the mineralized mechanism is favorable to understand the genesis of the deposit and to guide the prospecting in this area. Detailed studies on mineralogy, petrography and trace elements of fluorites from the deposit have been conducted in this paper. The results show that two stages of hydrothermal fluorite including metallogenic stage dark purple fluorite and post metallogenic stage purple fluorite have been identified, with the metallogenic stage dark purple fluorite closely associated with the uranium mineralization. The characteristics of trace elements and the REEs pattern are significantly different in two stage fluorites. The dark purple fluorite in the metallogenic stage is relatively enriched in Sr and Ba, while the purple fluorite in the post metallogenic stage is relatively enriched in REE and trace elements such as Co, Ni, Cu, Zn, Ga, Rb, Y, Zr, Nb, Mo, Cs, Pb, Th and U. The ΣREE of dark purple fluorite in the metallogenic stage ranges from 59.98×10-6 to 118.31×10-6, with a median value of 75.02×10-6, and the REE pattern is characterized by enriched LREE (LREE/HREE ratios median 5.06) and a strong fractionation between LREE and HREE ((La/Yb) N value median 12.24)), with moderate negative Eu anomaly (with median of 0.56), week Ce anomaly (with median of 0.99) and positive Y anomaly (with median of 2.21). The ΣREE of purple fluorite in the post metallogenic stage ranges from 194.12×10-6 to 207.67×10-6, with a median value of 195.55×10-6. The REE patterns of purple ?uorite is characterized by enriched LREE (LREE/HREE ratios median 4.76) and a relatively strong fractionation between LREE and HREE ((La/Yb) N value median 6.37)), with a well-pronounced negative Eu anomaly (with median of 0.09), positive Ce anomaly (with median of 1.33) and positive Y anomaly (with median of 1.90). Based on the comparison with the geochemical characteristics of the surrounding rocks and the pitchblende, two stages of fluorite (metallogenic stage dark purple fluorite and post metallogenic stage purple fluorite) in Haidewula uranium deposit were formed in the fluids with different sources. The metallogenic stage dark purple fluorite was formed in the acidic ore-forming ?uid rich in F- and Cl-, and maybe precipitated by the mixing mechanism of meteoric water with magmatic water in a reducing environment. The trace element geochemical characteristics of post metallogenic stage purple fluorite, such as with Ce positive anomaly and inheriting the Eu negative anomaly of the ore-bearing volcanic host rocks, indicated that the fluorite was formed in the oxidizing environment with higher proportion of meteoric water and higher oxygen fugacity and pH value in the fluid.
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Iron isotopic characteristics constraints and indicative significance of the Xiaohongshilazi Pb-Zn (Ag) deposit in Jilin Province

Wang Gaotian, Wang Da, Bai Feng, Xu Debing, Wang Guilong

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The Xiaohongshilazi Pb-Zn (Ag) deposit is a representative medium-sized deposit within the Jizhong-Yanbian copper-nickel polymetallic metallogenic belt, the main views for deposit types mainly include VMS type, medium-low temperature hydrothermal vein type, and exhalative deposits overprinted by hydrothermal fluid. In order to constrain the ore genesis, the Fe isotope characteristics of pyrite and pyrrhotite are systematically investigated. The overall δ56Fe values range from –0.82‰ to 1.00‰; Compared with other various type deposits, we have found that the Xiaohongshilazi Pb-Zn (Ag) deposit shows the characteristics of both hydrothermal and sedimentary deposits, hence the metallogenic hydrothermal fluid should be hot spring, and MVT type is most suitable. The δ56Fe values of pyrite gradually decrease from stage 1 (1.00‰) through stage 2 (0.21‰ ~ 0.83‰) to stage 3 (0.08‰ ~ 0.12‰); in comparison, the δ56Fe values of pyrrhotite gradually increase from stage 1 (–0.82‰) through stage 2 (–0.55‰ ~ 0.13‰) to stage 3 (–0.23‰ ~ –0.21‰), which is the typical Rayleigh fractionation characteristics. Within coexisting mineral pairs, the pyrrhotite is preferentially enriched in light Fe isotopes relative to pyrite, which is the same with previous studies. In addition, a Fe isotope fractionation model has also been established, which imply that the collected samples were correspond to the intermediate period (33.96% ~ 63.70%) of the whole mineralization process, while 63.59% of the metal resources related to the early period (0.00% ~ 33.96%) and late period (63.70%~ 100.00%) have not been discovered. In summary, the Fe isotopic compositions is mainly controlled by Rayleigh process, although the Fe isotopic evidence supported the MVT genesis, the geological characteristics are slightly different hence it should be classified as an MVT-like deposit; and there is still further prospecting potential within orefield.
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Study on the process of iron-aluminum differentiation in bauxite formation: a case study of the iron-aluminum rock series in the Jiujialu Formation of the Carboniferous System in Central Guizhou

Yang Ruidong, MO Hongcheng, LUO Chaokun, GAO Junbo, NI Xinran, Peng Rou, GAO Chuanqian, CHEN Jun, CHEN Jiyan

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Based on the study of the iron-aluminum rock series of the Jiujialu Formation in the Carboniferous System of Central Guizhou, as well as the sedimentary sequence, sedimentary structures, and geochemical analysis, it is concluded that iron-aluminum differentiation primarily occurred during the depositional period. The banded, clastic, and oolitic structures observed in the ferruginous rock indicate its depositional origin rather than post-depositional iron migration. Geochemical characteristics show distinct elemental compositions between the ferruginous rock and bauxite, suggesting differences in sediment sources and depositional environments during the depositional period. The proximity of high-iron bauxite deposits to source areas and the distance of low-iron bauxite deposits from source areas further support the conclusion that iron-aluminum differentiation primarily occurred during deposition. The iron-aluminum differentiation in the Jiujialu Formation is closely related to global paleoclimatic changes, particularly the transition from a hot and arid climate to a cold climate during the early Viséan period. The abrupt intensification of rainfall led to the leaching of iron-rich material from the weathered crust, which was transported in colloidal form and deposited in lakes and swamps, forming ferruginous rock. Subsequent heavy rainfall events resulted in flood events, during which aluminum-rich weathered crust was transported as debris flows into lakes or swamps, leading to the deposition of clastic bauxite as a product of these flood events.
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Sedimentary characteristics and geochemical constraints of borate deposits in salt lakes on Qinghai-Tibetan Plateau

Xiang Honglu, Fan QIshun, Li Qingkuan, Chen Tianyuan, Yang Haotian

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Boron is a strategic key non-metallic mineral in China, widely used in new energy, new materials, electronic information and other high-tech fields. The salt lake type borate deposits are mainly distributed on the Qinghai-Tibetan Plateau and the most important and promising boron resource type in China. Boron-rich salt lakes in the Qinghai-Tibetan Plateau show hydrochemical zones and differences of borate deposit types in different hydrochemical of salt lakes from south to north, but there is lack of comparative study of boron-rich salt lakes in different zones.This paper summarizes and compares the sedimentary characteristics of solid boron deposits and the differences of geochemical parameters of boron-rich brines in carbonate type (I region), sodium sulfate-magnesium sulfate subtype (II region) and magnesium sulfate-chloride type (III region) salt lakes on the Qinghai-Tibetan Plateau. The main conclusions are obtained as follows:① Borate minerals are mostly deposited directly on top of the clastic sediments, and present interactive multilayer deposition characteristics, indicating that the deposition of borate deposits requires brackish water recharge and hydrological environment changes, which accords with the theory of "Brine diluted into salt"；② The deposition of borax and ulexite is associated with a large number of mirabilite, and the deposition of pinnoite and Kurnakovite is accompanied by a large number of magnesium-bearing carbonate mineral (Hydromagnesite and dolomite), which indicates that the deposition of borax and ulexite requires the recharge of waters high in Na+, and that the deposition of pinnoite and Kurnakovite requires the recharge of waters high in Mg2+；③ The boron precipitation conditions of salt lakes inⅠ,Ⅱ, and Ⅲ zones are similar, as shown by the brine pH value of more than 8 and the B content of more than 400 mg/L; however, there are differences between different salt lakes in terms of TDS, Mg, and Na content；④ Combined with the chemical composition of borate deposits types mainly containing Na+ and Mg2+.The B×10-Na-Mg terminary equivalent diagram in zones Ⅰ, Ⅱ and Ⅲ shows that the equivalent of Na and B are in the range of 0.2-0.6 and 0.4-0.7, respectively, whereas there are some differences in the Mg equivalence values, with zones Ⅰ < 0.1, and zones Ⅱ and Ⅲ in the ranges of 0.1-0.4.
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Summary of the exploration achievements and gold mineralization of Jiaodong Xiling super large gold deposit

jia

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Jiaodong is the most important concentrated exploration area for gold deposits in China. During the 14th Five Year Plan period, Shandong gold geology and mineral exploration Co., Ltd. explored another super large gold deposit -- Xiling gold deposit between Sanshandao-Cangshang fault zone. Its accumulated detected gold resources reach 580t, with an average grade of 4.24 g/t, making it the largest single gold deposit discovered in China at present. It is located between the Sanshandao gold deposit and the northern sea area gold deposit. It is the deep extension and lateral part of the Sanshandao gold deposit in the northeast direction, and is connected to the northern sea area ore body in the deep. In fact, the three are actually the same ore body. Xiling gold ore body controls a maximum strike length of nearly 2000m and a maximum extension depth of 2057m; it is found that the ore body is in the form of "short handled axe" inclined to the Northeast in the horizontal direction, and has obvious echelon in the vertical distribution. The gold resources are mainly concentrated at the elevation of -1000 ~ -2200m; At the northeast end of the mining area, the ore body has extended to - 2600m, and continues to go deep. The thickness of the ore body becomes thinner, the grade is low, and the deep gold mineralization becomes weaker; The ore body extends from shallow to deep in multistage steps, which generally shows the characteristics of steep and gentle alternating echelon mineralization. Through the study of fluid inclusions in the deposit, it is found that the gold ore-forming fluid belongs to H2O-CO2-nacl fluid with medium temperature (199 ~ 347 ℃) and medium and low salinity (0.35 ~ 8.28 wt.%) rich in CO2, which is consistent with the large-scale gold ore-forming fluid in Jiaoxi North University, but slightly different in the process of gold deposit precipitation and migration. The precipitation mechanism of Xiling gold is mainly fluid immiscibility, and the temperature and salinity of the fluid in the main metallogenic period change most obviously, from the shallower part to the later stage of mineralization, The properties of ore-forming fluids tend to be more uniform. There is a certain coupling relationship between the emplacement of fluids and the spatial echelon mineralization. Gold mineralization is mainly concentrated in the second and third echelon spaces, corresponding to the middle and late stages of the mineralization stage. The study of S isotope shows that pyrite δ34S value has the trend of first increasing and then decreasing. The initial sulfur source of Xiling gold deposit may be closer to magmatic sulfur. In the process of mineralization, ore-forming materials and ore-forming fluids were mixed with other sources. The gold ore in the area has experienced strong assimilation, mixing and alteration metasomatism. The main element SiO2 is moderately acidic, with high Al2O3 and K2O and low Na2O、 TiO2、 MgO and CaO. It is peraluminous potassic basalt and high potassic calc-alkaline series granite. The ree distribution form is right-leaning type enriched in LREE, enriched in large ion lithophile elements (LILE) and depleted high field strength elements (HFSE), which has similar geochemical characteristics with island arc magmatites in extensional tectonic setting. Comprehensive studies have shown that,Xiling gold deposit belongs to altered rock type gold deposit formed by mesothermal magmatic hydrothermal filling metasomatism according to its genetic type. It was formed in the extensional tectonic background under the failure mechanism of North China Craton in the early Cretaceous. In the early Cretaceous, lithosphere thinning and asthenosphere upwelling caused large-scale magmatic activity. The coupling of structure, magma and fluid created large-scale gold mineralization in this area.
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The characteristics and origin of the pre-Sinian rift in the Sichuan Basin

Tang Hao, Wu Guanghui, Zou Yu, Su Chen, Dai lan, zhang chen, Ma Bingshan

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The Neoproterozoic supercontinent breakup is of significant role in the origin of the rift basin and its hydrocarbon on Earth. However, there is still debate on whether the superplume or subduction process has triggered the rift basin. The largest Sinian gasfiled in China has been found along the Deyang-Anyue rift in the Sichuan Basin. Owing to absence of geological data and low-resolution seismic data, it is an enigma on the origin and distribution of the pre-Sinian rifts in the ultra-deep subsurface. Together with seismic interpretation and compiled geochemical data, we discuss the characteristics and mechanism of the pre-Sinian rift in the Sichuan Basin. The results show that: (1) NE-trending Pre-Sinian rifts developed well with more than 5000 m thick deposits in the Sichuan Basin, which are different in rift architecture and distribution from the Sinian depression to show a Pre-Sinian tectonic discontinuity; (2) the ?Hf isotope values of the Neoproterozoic zircons show a distinct pattern from a decreased trend to an increased trend, and present a tectonic transition period at ca. 830~780 Ma; (3) the Pre-Sinian rifting initiated during the transition period was consistent subduction process rather than mantle plume process. In conclusion, the mid-Neoproterozoic transitional subduction has resulted in the distributed deep Pre-Sinian rifts in the Sichuan Basin, which is a new favorable hydrocarbon exploration frontier.
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Jurassic anatexis and granite genesis in Amdo area,Northern Tibet

jianzhenzhu, pengyinbiao, jiangxingzhou, gaoxiangyu, jiwentao, lichuanzhi, yushengyao

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Abstract:

The Ando microland massif in Tibet, as a microland massif within the Bangong Lake-Nujiang River suture zone, has recorded multiple phases of tectonothermal events since the Neoproterozoic-Mesozoic era, and is an ideal object for the study of the genesis of the deep-melt-granitoids. In order to reveal the characteristics of the fluid/melt activities during the subduction-folding process of the oceanic plate, a comprehensive study was carried out herein, combining the whole-rock geochemistry, systematic petrology, zircon internal structure, zircon U-Pb ages, and Lu-Hf isotopes. A comprehensive study was carried out. Petrographic observations show that the mixed gneiss retains key field macro- and microscopic evidence of deep melting: (1) light and dark bodies are interbedded in a laminated distribution, accompanied by weak fold deformation; (2) there are assemblages of fine grains at the boundaries of quartz and potash feldspar, and irregular crystallization of potash feldspars from edge to middle; (3) plagioclase feldspar and potash feldspar boundaries show highly acicular, elongate, or wedge-shaped quartz and feldspar grains, with "bead" structures along the quartz and feldspar grain boundaries. The cathodoluminescence images and zircon U-Pb dating results show that the zircons in the mixed-rock gneisses have a distinct core-rim structure, with a distinctive oscillatory ring in the zircon cores, which gives a magma crystallization age of ~510 Ma, and narrow metamorphic or deep-melting rims in the rims. The zircon in the light-colored body has obvious core-rim structure, and the CL image shows that the zircon core is highly luminous with oscillatory ring band, which may be inherited magmatic zircon, and the zircon rims show deep melting features such as weakly fractional bands of grayish to dark color or no fractional bands, and the age of the core is ~510-470 Ma representing the age of protolithic crystallization, and the rims have an age of ~184 Ma indicating the age of melt crystallization. The zircons of the granodiorite have typical magmatic zircon characteristics, with a magmatic crystallization age of ~180 Ma, which agrees with the age of the light-colored body within the error range. The εHf(184) values of deep-melting diagenetic zircons in the light-colored body range from -5.0 to -3.3, while those of granodiorite magmatic zircons range from -10.97 to -5.21. Whole-rock geochemical analyses indicate that Fe2O3T, MgO, TiO2, CaO, and REEs are almost completely retained in the dark-colored body, while a large number of LILEs (Rb, Sr, K, Ba ) are to the light-colored body. The light-colored body is divided into Type I light-colored body and Type II light-colored body according to the whole-rock REE characteristics and whether it carries residual hornblende, in which Type I light-colored body has higher total rare earth content and negative Eu anomaly, while Type II light-colored body has lower total rare earth content and positive Eu anomaly; the trend of the distribution of rare earths (REEs) of granodiorite eclogites is consistent with that of Type I light-colored with an enrichment of the large ionic proximate elements (Rb, Ba, and Th) and a Negative Eu anomalies; the synthesis of the existing regional data and the field relationship, microstructure, chronology and geochemical results obtained in this paper indicate that the black cloud plagioclase gneisses of the Ando microterrane occurred in the subduction and folding stage of the hydrous partial melting involving black mica, and that the type I light-colored bodies in the mixed rocks formed the contemporaneous granodiorite bodies through large-scale convergence, migratory evolution and encroachment.
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Re-discussion on genetic type of the Daliang Uranium deposit at Motianling: evidence from elemental and isotopic compositions of pitchblende

Wangkaixing, Ye fancheng, Zhu kunhe, zhangjian, Liux iaodong, Tan shuang, Sun Liqiang, Yang Jianjun

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The Daliang uranium deposit is located in the Motianling pluton, northern Guangxi Province. It represents the oldest uranium deposit that related to granitoid in South China. Recent studies indicate that the Daliang uranium deposit exhibits distinct characteristics from typical hydrothermal uranium deposits related to the Mesozoic granites in South China, suggesting the possibility of a different deposit genetic type. The elemental chemistry and isotopic compositions of pitchblende are favorable tools for determining the mineralization age and exploring the deposit genesis type. Therefore, based on previous research, this study conducts the chemical composition and isotopic dating of pitchblende to determine the mineralization age and genesis type of the Daliang uranium deposit. The research results demonstrate that the pitchblende in the Daliang deposit exhibits features such as insignificant fractionation between LREE and HREE with weak negative Eu anomaly, which are similar to typical pitchblende in synmetamorphic uranium deposits. Using EMPA U-Th-Pb chemical dating and LA-ICP-MS U-Pb isotopic dating, the mineralization ages of the Daliang uranium deposit are determined to be 378 Ma and 376±4 Ma (MSWD=0.62), respectively, coupled with regional ductile deformation events, indicating that the deposit formed during the Late Devonian and suggesting a connection to regional ductile deformation. Combining previous studies on the high salinity of the mineralizing fluids in the Daliang uranium deposit (average 19% NaCl equivalent) and the stable isotopic constraints on the fluid source, it can be inferred that the Daliang deposit is likely not a traditional hydrothermal vein-type uranium deposit associated with granite but should be classified as a synmetamorphic uranium deposit. During the process of forward shearing detachment at Motianling during the Devonian period, when the uplifted brittle-ductile shear zone formed in the middle to lower strata reaches shallow depths, the granitic mylonite enters the brittle-ductile deformation zone. The mineralizing fluids extract uranium from the granite and precipitate in the brittle-ductile deformation zone, forming the Daliang metasomatic uranium deposit. This study establishes, for the first time, the presence of synmetamorphic uranium deposits in granites of South China. This implies the potential involvement of different genetic models and processes in the hydrothermal uranium deposits of South China. This finding holds significant importance for future uranium exploration and research in South China and deserves attention.
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Chemical characteristics of pyrochlore in carbonate of the Huayangchuan uranium-niobium deposit and its significance for mineralization

Huang Hui, Pan Jiayong, Wang Kaixing, Zhong Fujun, Wan Jianjun, Wu Bin, Yin Shuo, Yan Jie

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Abstract: The Huayangchuan deposit in Shaanxi Province is located in the Xiaoqinling metallogenic belt in contact between the North China Craton and the Qinling orogenic belt. It is a world-class uranium and niobium polymetallic deposit related to carbonatite, in which pyrochlore is the major U and Nb-bearing mineral. Although the Huayangchuan metallogenic mechanism has been well studied, the magmatic-hydrothermal evolution process of the deposit and its relationship with mineralization were poorly understood. Hereby, this paper study mineralogy, chemical composition and evolution characteristics of two types of primary pyrochlore (pcl Ⅰ and pcl Ⅱ) and three types of altered pyrochlore (pcl Ⅰ alt1, pcl Ⅰ alt2 and pcl Ⅱ alt) in the Huayangchuan deposit. The results show uranium and niobium mineralization in Huayangchuan carbonatite is closely related to the Late Triassic magmatism. It was related to a mantle-derived, initially U-rich carbonatitic magma, which has been further enriched in U by crystallization differentiation and formed the primary (magmatic) pyrochlore (pcl I), primary pyrochlore (pcl Ⅱ) and primary uraninite (Ur1) through partial melting from the mantle. In the early Cretaceous, the carbonatite in Huayangchuan were subjected to high-temperature hydrothermal alteration, and part of Nb and U released from the early pyrochlore (pcl Ⅰ) were dissolved and reactivated by the high temperature high-F fluid, which formed the primary uranite (Ur2), the altered pyrochlore (pcl Ⅰ alt1) and the secondary titanite (Ttn2). The primary pyrochlore (pcl Ⅰ) and primary pyrochlore (pcl Ⅱ) can be replaced by the altered pyrochlore pcl Ⅰ alt2 and altered pyrochlore pcl Ⅱ alt in the post ore low-temperature alteration. These results indicate that two magmatic-hydrothermal uranium-niobium mineralization and one post-mineralization low-temperature hydrothermal alteration occurred in Huayangchuan deposit during late Triassic and early Cretaceous.
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Discussion on S-Pb-H-O-He-Ar isotope composition and genesis of the Sanhetun gold deposit in Heilongjiang Province

liubaoshan

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Sanhetun gold deposit is located in Nenjiang County, Heilongjiang Province. The ore body occurs in the late Triassic granitic mylonite, near the contact zone between the volcanic rocks of the lower Cretaceous Guanghua Formation and the late Triassic granitic mylonite. In order to discuss the source of ore-forming fluid, this work systematically studied the S, Pb, H, O isotopes and inert gas He, Ar isotopic compositions in different minerals collected. Stable isotope results show that: δ34S is between -4.4‰~4.9 ‰，which is similar to meteorite sulfur δ34S value,reflects the contribution of sulfur from deep magma; 206Pb/204Pb of Pyrite =17.284-18~180290，207Pb/204Pb=15.505~15.561,208Pb/204Pb=37.656~38.116; 206Pb/204Pb of Quartz=18.206~ 18.449,207Pb/204Pb=15.526~15.652,208Pb/204Pb=38.050~38.648, which indicates that the ore-forming material mainly comes from mantle; H, O isotopes of Quartz δ DV-SMOW value is - 77.5 ‰~- 96.3 ‰, δ 18OV-SMOW is 7.4 ‰~11.6 ‰, δ18OH2O is - 0.2 ‰~4.8 ‰, which reflects that the ore-forming fluid mainly comes from atmospheric precipitation, and some magmatic water also participates; The 3He/4He ratio of Pyrite fluid inclusions is 1.19～1.54R/Ra, tens to more than hundreds times higher than the 3He/4He ratio of the crust, but obviously lower than the 3He/4He ratio of mantle fluid; 40Ar/36Ar=608.5～922.6, higher than the 40Ar/36Ar composition of crustal fluid (40Ar/36Ar＞295.5);The 40Ar*/4He ratio is 0.14～1.56, with an average value of 0.95. The 40Ar*/4He (0.14) of SHT19 sample data is close to the 40Ar*/4He (0.2) fluid of the crust, and the 40Ar */4He (0.88～1.56) of other samples is much higher than the mantle (0.33～0.56) fluid, indicating that the ore-forming fluid may be mainly meteoric water, but also the crust and deep mantle fluid. According to the regional metallogenic epoch, the Sanhetun gold deposit was formed in the late Early Cretaceous, and the source of ore-forming materials was closely related to the magmatic activity in the Guanghua period of the Early Cretaceous.
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The deposit types, spatial and temporal distribution and prospecting direction of rare earth deposits in China

Yu Jinjie, Chen Shaocong, Chen Xiaodan

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Rare earth element (REE) deposits in China can be categorized into the hard rock-type, ion adsorption-type, and placer REE deposits. The hard rock-type, ion adsorption-type, and placer REE deposits account for 96.4%, 3.2% and 0.5% of the total REE resource of China, respectively. The REE deposits in China are composed of 12 metallogenic zones, and the peak periods of mineralization are mesoproterozoic and Cenozoic. The former is represented by Bayan Obo ore deposit, while the latter is represented by the REE deposits of the Mianing-Dechang metallogenic zone and ion adsorption-type REE deposits in six provinces of southern China. The available rare earth deposits in China are carbonatite and alkaline rock-related and ion adsorption type REE deposits. The former is the source of LREE and the latter is the source of HREE. The controlling factors of carbonatite and alkaline rock-related REE deposits include rifts or collision-post-collision tectonic settings along craton margins, regional deep faults, and the magmas and post-magma hydrothermal evolution. The controlling factors of ion adsorption-type REE deposits include parent rocks, favorable exogenetic factors including quasi-equilibrium between denudation and exhumation at regional scales, local geomorphology dominated by low-lying gentle slopes, adequate rainfall, and favorable groundwater conditions. In this paper, the general metallogenic models of carbonatite and alkaline rock-type and ion adsorption-type REE deposits are recommended. The prospecting of carbonate rock and alkaline rock-type REE deposits Sis concentrated in the depth and edges of known deposits, but the search for hard rock-type heavy rare earth deposit in Xingmeng and Boziguer-Yilanlik metallogenic belts should not be ignored. Southern Jiangxi and northern Guangdong provinces are the key areas to search for ion adsorption-type HREE deposits.
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Volume 99,2025 Issue 4

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