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2025,99(2):297-319, DOI: 10.1111/1755-6724.15292
Abstract:
East Asian continental tectonics challenges the plate tectonics paradigm with its diffuse intraplate deformation, magmatism, and earthquakes. Despite extensive studies, fundamental questions persist. This review examines ten critical questions of East Asian tectonics, including the thickness of the continental lithosphere, the origin of the North–South Gravity Lineament, and the northern extent of the Indian plate beneath the Tibetan Plateau. Additional questions address the Tibetan Plateau's lateral growth, the Tianshan mountain building, the mantle flow in response to the Indo-Asian collision, and the formation of the Shanxi Rift. The review also explores the subduction along the eastern margins of the East Asian Continent and the origins of the Changbaishan volcanic field, the destruction of the North China Craton, and the development of the Mesozoic Large Granitic Province in South China. Originally presented at the DEEP2024 workshop to stimulate discussion of how SinoProbe-II research initiatives could advance our understanding of Asian tectonics, this review provides context for each question, summarizes current knowledge, and identifies promising research directions.
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YU Kaifeng，WU Wenhao，SUN Wei，CHEN Jun，WANG Xuri
2025,99(2):320-331, DOI: 10.1111/1755-6724.15288
Abstract:
Twelve new dinosaur teeth have recently been recovered from three localities in the Upper Cretaceous Nenjiang Formation of the Songliao Basin. Although fragmentary, the material offers enough evidence to identify the following taxa: tyrannosaurids, dromaeosaurines, velociraptorines, hadrosauroids, and titanosaurs. In addition to the previously known dinosaurs from the basin, several new ones have been identified, extending the paleogeographic range of related taxa. The discovery of these new fossil remains provides valuable insights into dinosaur diversity and sheds light on the terrestrial ecosystem during the Late Cretaceous in the Songliao Basin.
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Fikret GOKTAS，Serdar MAYDA，Mehmet Cihat ALCICEK
2025,99(2):332-351, DOI: 10.1111/1755-6724.15279
Abstract:
In a re-examination of the Neogene stratigraphy of the U?ak, Güre, and Selendi basins of western Anatolia, western Turkey, the stratigraphic position of the previously defined ?nay Group is revised, which was previously considered to be of the Middle Miocene age. Based on mammalian biochronology and stratigraphic relationships, two sequences are identified, separated by conformable/transitional contacts within the former group: the Middle Miocene Güre Group is composed of the Fak?l? Formation, characterized by alluvial fan deposits, and the lacustrine Derbent Formation. Radiometric dating of alkaline volcanics laterally associated with Güre Group sediments in the U?ak and Güre basins, and mammalian fossils re-evaluated into the MN5-6 biozones in the Selendi Basin, indicate early Middle Miocene. Considering the stratigraphic relationship with the overlying early Late Miocene ?nay Group as redefined, we estimate that the Güre Group was deposited in the Middle Miocene. The ?nay Group is characterized by a lateral–vertical transition from alluvial deposits of the Ahmetler Formation to the overlying lacustrine Ulubey Formation. An MN9-10 fauna, containing deinotheres, was found within the latter formation.
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2025,99(2):352-369, DOI: 10.1111/1755-6724.15282
Abstract:
The approximately 3000 km long Tan–Lu fault zone (TLFZ) in East Asia is the longest continental strike-slip fault zone in the world and exemplifies how such a fault zone forms and propagates on a continental scale. Structural and geochronological data from the TLFZ and surrounding regions indicate that the fault zone originated as NE/SW-striking sinistral ductile shear zones along an oblique continental convergence margin during the Triassic indentation collision between the North China Craton and the Yangtze Block. The Triassic fault zone, with a total length of about 720 km between the Dabie and Sulu orogens, exhibited an apparent sinistral offset of approximately 300 km along the TLFZ. The second stage of sinistral movement occurred in the earliest Late Jurassic, reactivating the pre-existing southern segment and propagating northwards to the southern coastline of present-day Bohai Bay, as well as forming a significant portion of the Dunhua–Mishan fault zone. The third stage of sinistral movement, in the earliest Early Cretaceous, was the most intense strike-slip movement of the Mesozoic, leading to the complete linkage of the TLFZ. This stage included further northward propagation of the southern–middle segment, both southward and northward propagation of the Dunhua–Mishan fault zone, as well as the formation of the entire Yilan–Yitong fault zone. The fourth stage, in the earliest Late Cretaceous, involved the reactivation of the entire TLFZ. Following its Triassic origin due to the indentation collision, the subduction of the Paleo-Pacific Plate and the subduction and closure of the Mongol–Okhotsk Ocean were responsible for the multi-stage sinistral movements from the Late Jurassic to the Cretaceous. The evolution of the TLFZ demonstrates that a continental-scale strike-slip fault zone (>1000 km long) forms through multiple stages of propagation and linkage in dynamic settings of plate convergence.
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Farid MAKROUM，Mohamed BADAWI，Kurt STUWE，Norbert NEMETH，Mahmoud ABDELATIF，Ahmed SHALABY
2025,99(2):370-393, DOI: 10.1111/1755-6724.15290
Abstract:
The Barud gneissic dome complex is situated along the ENE-trending dextral shear zone of the Qena–Safaga Line that serves as a significant tectonic boundary between the basement terrains of the Northern and Central Eastern Desert. These terrains exhibit distinct differences in crustal composition and deformation style. The Northern Eastern Desert and its extension into Sinai are predominantly composed of gneissic granites that are intruded by large batholiths of calc-alkaline and alkaline granites. Conversely, the Central and Southern Eastern Desert are commonly blanketed by a carapace of ophiolite-bearing volcano-sedimentary rocks of the Pan-African cover nappes. These northern terrains, just north of the Barud dome complex, the crust underwent significant NW–SE regional crustal extension across the Qena–Safaga Line, which sharply delineates the northern limit of the transpressional deformations linked to the Najd fault system in the Central and Southern Eastern Desert. Through comprehensive geological mapping and the integration of various geophysical, geochemical and geochronological data, this paper offers explanations for the contrasting geological features of the basement terrains on both sides of the Qena–Safaga Line and its analogous Fatira Shear Zone that plays a significant role in tectonic modeling of the Barud dome complex region. The Barud gneissic protolith experienced crustal shortening approximately 697 million years ago in the NW–SE direction, initiating dextral motion along the Fatira Shear Zone. Large batholiths of granodiorite/tonalite complex intruded the Barud gneissic dome protolith around 630 million years ago along the Qena–Safaga Line, at relatively shallow crustal depths, following the same orientation as the earlier shortening direction. Ongoing magmatic activity along the Qena–Safaga Line indicates intense magmatic underplating, resulting in significant intrusions of granodioritic melts into the early rifted crust of the Northern Eastern Desert and Sinai terrains. The crust of these northern terrains likely underwent isostatic compensation through uplifting and subsequent erosion. The disappearance of ophiolite-bearing belts and the presence of Paleo- to Mesoproterozoic continental-derived cobbles and ignimbrites in Sinai metasedimentary belts and Northern Eastern Desert molasse basins suggest that the northern terrains, located north of the Qena–Safaga Line, originated as a cohesive, thin continental crust that rifted off the eastern passive margin of the Sahara Metacraton during the early Neoproterozoic rifting of the Rodinia supercontinent.
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LONG Kangjie，FENG Qianqian，TENGER Borjigin，QIU Nansheng，YU Taiyan
2025,99(2):394-408, DOI: 10.1111/1755-6724.15287
Abstract:
Apatite (U-Th)/He and fission track dating and tectono-thermal history modeling were used to reconstruct the Meso–Cenozoic tectonic evolution of the Huangling paleo-uplift in the Middle Yangtze Block, South China. The tectono-thermal evolution showed different tectonic exhumation/subsidence processes in the tectonic evolution of the foreland basin. The apatite (U-Th)/He ages ranged from 31.3 to 77.8 Ma, recording the thermal events of the Cenozoic Himalayan movement and indicating progressive exhumation extending from the southeast to the northwest. The thermal information of the Mesozoic Yanshan movement period was recorded by the apatite fission track age with a pooled age of 93.8 to 147 Ma. The exhumation of the Huangling paleo-uplift began in the Late Jurassic. The tectono-thermal evolution was characterized by a rapid uplift during 140–115 Ma, subsidence during 115–60 Ma, a rapid uplift during 40–30 Ma, and a slow uplift from 30 Ma to the present. The western Hunan–Hubei Depression was exhumed in the Middle Jurassic, and the tectono-thermal evolution was characterized by a rapid uplift during 160–135 Ma, a slow uplift during 135–50 Ma, a rapid uplift during 50–25 Ma, and a slow uplift from 25 Ma to the present. This Cenozoic exhumation was a response to the far field effect of the eastward growth of the Tibetan Plateau. The Cretaceous basins exposed in the surrounding areas of the Huangling paleo-uplift (Zigui basin, Yichang slope, and Huaguoping synclinorium) are foreland basins formed by the bi-directional compression of the Qinling–Dabie orogenic belt and the Xuefengshan intracontinental deformation system.
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2025,99(2):409-424, DOI: 10.1111/1755-6724.15254
Abstract:
Fragments of Proto-Tethyan oceanic lithosphere are well-preserved along the southern belt of the North Qilian suture, and the origin and emplacement of these ophiolites have become subjects of intense debate. In this study, we integrate field observations, mineralogical and geochemical analyses, zircon U-Pb dating, and isotopic data to investigate the Yanglong ophiolite. The Yanglong ophiolitic rocks are found as tectonic slices resting on the Neoproterozoic sedimentary and volcanic rocks. These rocks are composed of Cambrian serpentinized peridotite, gabbro, dolerite, and rodingite. The spinels in the serpentinized peridotites have variable Cr# values (21, 38–46, and 59–61) and display affinity to those in abyssal and forearc peridotites. The dolerites show slight enrichment in Th and have elevated (La/Sm)N ratios (1.19–2.01), indicating a subduction-related geochemical affinity. The Yanglong ophiolitic rocks have positive zircon εHf(t) values (+10.3 to +18.4) and whole-rock εNd(t) values (+5.3 to +6.7) indicating derivation from partial melting of a depleted mantle source. These results, together with the regional geology, collectively suggest that the Yanglong ophiolite was generated in a forearc setting during the Early Cambrian northward intra-oceanic subduction. It was emplaced onto the Central Qilian Block during the subsequent arc–continent collision, no later than the Early Ordovician.
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2025,99(2):425-440, DOI: 10.1111/1755-6724.15284
Abstract:
The Qinling orogenic belt in central China underwent long-term tectonic evolution during an amalgamation between the North China and South China cratons. However, intense compressional deformation and uplift erosion resulted in the transformation and disappearance of much geological record from the Qinling orogenic belt, and the tectonic evolution of this belt remains poorly constrained during the Triassic. Located in the northernmost margin of the South China Craton, the Sichuan Basin preserves the complete Triassic sedimentary succession, and can provide significant information for understanding the Triassic tectonic evolution of the Qinling orogenic belt. We present detrital zircon U-Pb dating, trace element and in situ Lu-Hf isotope data for the Middle Triassic Leikoupo Formation and the Late Triassic Xujiahe Formation samples from the eastern Sichuan Basin, South China. The detrital zircon U-Pb ages of the Leikoupo Formation show seven age clusters of 280–242, 350–300, 500–400, 1000–800, 2000–1750, 2100–2000 and 2600–2400 Ma, while those of the Xujiahe Formation show five age clusters of 300–200, 500–350, 1050–950, 2000–1750 and 2600–2400 Ma. Combined with published paleocurrent and paleogeographic data, the sediments of the Leikoupo Formation are interpreted to be sourced from the North China Craton, Yangtze Craton and North Qinling orogenic belt, and the potential main source regions of the Xujiahe Formation included the South and North Qinling orogenic belts. Provenance analysis indicates that the North Qinling orogenic belt was in inherited uplift and coeval denudation in the Middle Triassic. The proportion of the detritus formed in the South Qinling orogenic belt increases gradually from the Leikoupo to Xujiahe formations. This significant provenance change indicates that rapid tectonic uplift and extensive denudation of the South Qinling orogenic belt occurred in the early Late Triassic, which is related to the collision between the North China and South China cratons during the Triassic.
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2025,99(2):441-458, DOI: 10.1111/1755-6724.15280
Abstract:
Large-scale Cenozoic alkali-rich magmatic rocks are exposed at the eastern margin of Tibet due to the interaction between the Indian and Eurasian plates. However, their petrogenesis and associated geodynamic processes remain poorly understood. We analyzed the Xifanping porphyries in the Sanjiang orogenic belt to provide new insights. Our study shows a successive assembly of porphyry intrusions during three magmatic episodes. The magnitude and duration of the magmatic activities diminished sequentially, and mineralization occurred during the intermediate phase. Geochemically, the Xifangping porphyries display an adakitic affinity. According to zircon Hf isotope data, we propose that these porphyries originated from the partial melting of the thickened mafic lower crust beneath the western Yangtze Craton in response to lithospheric extension and asthenospheric upwelling. Analogous to the coeval alkali-rich porphyries in western Yunnan, the petrogenetic model of the Xifanping porphyries indicates regional north–south and east–west fractures caused by the clockwise rotation of the continental lithosphere and the Jinshajiang–Red River strike-slip during the post-collision phase of the India–Eurasia collision. In this context, we argue that the collision in eastern Tibet may have extended eastward to southwestern Sichuan during the post-collision period, persisting until approximately 30 Ma.
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LIU Yu，JIANG Biao，WU Liwen，ZUO Yushan，LIU Zhao，LIU Haitao
2025,99(2):459-472, DOI: 10.1111/1755-6724.15215
Abstract:
The Shuangjianzishan deposit is a typical magmatic-hydrothermal deposit located in the southern Great Xing'an Range. Recent investigations have identified significant copper and tin mineralization at depth within the Shuangjianzishan deposit; however, the coupling relationship between magmatic emplacement and mineralization processes remains debated. This study presents whole-rock geochemistry, zircon LA-ICP-MS U-Pb dating, and zircon Hf isotope analyses of granite from the northern Shuangjianzishan deposit. The analysis results indicate the granite crystallized between 252.3 and 257.9 Ma, corresponding to Late Permian magmatic activity. The granite displays εHf(t) = 5.95–14.87, and tDM2 = 333–900 Ma. Geochemically, the granite is rich in Si and Al, with high K, classified as a calc-alkaline, weakly peraluminous rock. LREEs are enriched, while HREEs are depleted, and a slight negative Eu anomaly, all of which are consistent with A-type granite characteristics. The Hercynian granite in the Shuangjianzishan deposit formed during the latter or post-collisional stages of the collision orogeny following the closure of the Paleo-Asian Ocean in the late Paleozoic era. The material source indicates a mixed origin, involving both crust and mantle contributions. The granite is also enriched in Cu, Pb, and Zn, suggesting its potential role as an ore-forming material source for the Shuangjianzishan deposit. This study proposes a potential link between Hercynian magmatism and mineralization at the Shuangjianzishan deposit for the first time, suggesting that multistage metallogenesis may be a response to successive magmatic events from Hercynian to Yanshanian periods in the mining area.
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LUO Xinyu，LIU Biao，KONG Hua，JIANG Hua，WU Qianhong，YANG Jiehua，Safiyanu Muhammad ELATIKPO
2025,99(2):473-498, DOI: 10.1111/1755-6724.15286
Abstract:
The Late Cretaceous Jiepailing granitoids, located at the central Nanling Range in South China, are closely associated with significant Sn-Li-Be-F polymetallic metallogeny. The Jiepailing granitoids mainly consist of granitic porphyry and zinnwaldite granite. The two granitoids have an A-type affinity, showing elevated Rb/Sr ratios and significant depletions in Ba, Sr and P. Integrated zircon and monazite U-Pb dating results suggest that granitic porphyry and zinnwaldite granite were emplaced at ~89 Ma and ~94 Ma, respectively. The low Ce4+/Ce3+ ratios of the Jiepailing granitoids, together with significant negative Eu anomalies of the zircons, indicate that their formation occurred under conditions of reduced oxygen fugacity. Through the analysis of zircon Hf-O and whole-rock Nd isotopes, it has been determined that both stages of the Jiepailing granitoids originated in the lower-middle Mesoproterozoic crustal basement [εNd(t) = ?5.33 to ?4.96, tCDM(Nd) = 1289–1234 Ma, εHf(t) = ?4.13 to +2.22, tCDM(Hf) = 1418–1015 Ma and δ18OZrc = 6.33‰–7.72‰], with the involvement of mantle-derived materials. Both granitic porphyry and zinnwaldite granite exhibit elevated concentrations of fluorine (F), with the positive correlation between F and Sn emphasizing the crucial role of high F sources in tin mineralization. Drawing upon the study of the Late Cretaceous magma systems in southern Hunan and through comparison with the mineralized granites observed in coastal regions during the Late Cretaceous, a genetic model for the mineralized granites in the Nanling region is developed. When the Paleo-Pacific Plate retreated to the coastal region, the continental crust in southern China underwent extensional thinning and asthenospheric upwelling due to gravitational collapse. Such processes resulted in the partial melting of the middle–lower crustal metamorphic sedimentary basement and the subsequent formation of F-rich granitic magmas, related to tin mineralization.
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2025,99(2):499-521, DOI: 10.1111/1755-6724.15291
Abstract:
Controversy is ongoing regarding the relationship between ore formation and the structural evolution of the Hadamengou gold deposit. To address this issue, we conducted a comprehensive investigation of mineralization-related structures, geochronology and Fe isotopes. From the perspective of spatial evolution, hydrothermal fluids originating from the Shadegai and Xishadegai plutons have extracted accumulated ore-forming elements from the Wulashan Group (Ar2WL) and then evolved, initiating at Exploration Line 11 and migrating eastwards and westwards along the EW-trending thrust fault system to form orebodies. From the temporal evolution standpoint, the Wulashan Group (Ar2WL) experienced diagenesis (2591.00 Ma to 2204.00 Ma) and metamorphism (2074.00 Ma to 1625.00 Ma) from late Neoarchean to early Paleoproterozoic, when ore-forming materials were initially accumulated; in the early Paleozoic (440.71 Ma to 425.00 Ma), the collision led to the formation of early-stage EW-trending imbricated thrust faults, which established a fundamental structural framework for the orefield and further accumulated ore-forming materials; from the late Paleozoic to the Mesozoic, multiple subsequent episodes of regional tectonic-magmatic-hydrothermal events have superimposed, modified and reactivated the thrust fault system. Notably, the Triassic period, particularly between 245.00 Ma and 217.90 Ma, is considered to be a primary ore-forming stage. In summary, the intricate relationship between ore-formation and structural evolution has been fundamentally elucidated.
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WANG Xuhui，LANG Xinghai，WU Changyi，DENG Yulin，Robert MORITZ
2025,99(2):522-531, DOI: 10.1111/1755-6724.15283
Abstract:
The key factor that controls the genesis of porphyry Cu deposits (PCDs) in collisional orogens remains a debated topic. This study employs whole-rock La/Yb proxies to quantitatively constrain the spatial and temporal variations in crustal thickness of the South Armenian–Iranian magmatic belt (SAIMB) within the Zagros orogen (central Tethys region) since the Eocene. Our results show that rapid crustal thickening occurred first in the NW section of the SAIMB at ~35 Ma, then propagated southeastward into the central and SE sections at ~25 Ma and 20 Ma, respectively, indicating that the Arabia–Eurasia collision was diachronous. The formation of the large and giant collision-related PCDs in the SAIMB might have been controlled by the collision process because they developed first in the NW section of the SAIMB and subsequently propagated southeastward into the central and SE sections. More importantly, crustal thickness mapping shows that the PCDs are preferentially developed in the thickened crust areas (>50 km). Our findings propose that thickened crust is critical for the formation of the PCDs in collisional orogens by promoting Fe2+-rich minerals as a fractionating phase, driving magmatic auto-oxidation and releasing Cu into the magmas. The Cu is then partitioned into magmatic fluids, sustaining the porphyry systems. Furthermore, our research highlights that the thickened crust hosting PCDs was characterized by a previously thinner crust (<40 km), where magmas had low oxygen fugacity due to the absence of the auto-oxidation process. Consequently, chalcophile elements (e.g., Cu) efficiently separated from the melt through sulfide segregation, forming large Cu-bearing lower-crustal cumulates. These cumulates can be mobilized with an increase in oxygen fugacity, incorporating into subsequent porphyry mineralization. We thus propose that the crustal thickness evolution over time controls the formation of the PCDs in collisional orogens. There are two essential stages in the collision-related PCDs formation: the first is high-flux magmatism in the thin crustal setting (<40 km), leading to metal-fertilized lower crust through sulfide segregation, and the second is the intracrustal auto-oxidation during crustal thickening (>50 km) which facilitates pre-enriched sulfides in the lower crust to re-dissolve, releasing Cu into the magmas.
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2025,99(2):532-552, DOI: 10.1111/1755-6724.15281
Abstract:
Although previous researchers have attempted to decipher ore genesis and mineralization in the Erdaokan Ag-Pb-Zn deposit, some uncertainties regarding the mineralization process and evolution of both ore-forming fluids and magnetite types still need to be addressed. In this study, we obtained new EPMA, LA-ICP-MS, and in situ Fe isotope data from magnetite from the Erdaokan deposit, in order to better understand the mineralization mechanism and evolution of both magnetite and the ore-forming fluids. Our results identified seven types of magnetite at Erdaokan: disseminated magnetite (Mag1), coarse-grained magnetite (Mag2a), radial magnetite (Mag2b), fragmented fine-grained magnetite (Mag2c), vermicular gel magnetite (Mag3a1 and Mag3a2), colloidal magnetite (Mag3b) and dark gray magnetite (Mag4). All of the magnetite types were hydrothermal in origin and generally low in Ti (<400 ppm) and Ni (<800 ppm), while being enriched in light Fe isotopes (δ56Fe ranging from ?1.54‰ to ?0.06‰). However, they exhibit different geochemical signatures and are thus classified into high-manganese magnetite (Mag1, MnO > 5 wt%), low-silicon magnetite (Mag2a-c, SiO2 < 1 wt%), high-silicon magnetite (Mag3a-b, SiO2 from 1 to 7 wt%) and high-silicon-manganese magnetite (Mag4, SiO2 > 1 wt%, MnO > 0.2 wt% ), each being formed within distinct hydrothermal environments. Based on mineralogy, elemental geochemistry, Fe isotopes, temperature trends, TMg-mag and (Ti + V) vs. (Al + Mn) diagrams, we propose that the Erdaokan Ag-Pb-Zn deposit underwent multi-stage mineralization, which can be broken down into four stages and nine sub-stages. Mag1, Mag2a-c, Mag3a-b and Mag4 were formed during the first sub-stage of each of the four stages, respectively. Additionally, fluid mixing, cooling and depressurization boiling were identified as the main mechanisms for mineral precipitation. The enrichment of Ag was significantly enhanced by the superposition of multi-stage ore-forming hydrothermal fluids in the Erdaokan Ag-Pb-Zn deposit.
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Jyoti Sankar SATAPATHY，Sahendra SINGH，Prabodha Ranjan SAHOO
2025,99(2):553-567, DOI: 10.1111/1755-6724.15289
Abstract:
Emerald mineralization from the Bahutiya and Gurabanda areas of Jharkhand in the eastern part of India is a recent discovery. In this deposit, emerald mineralization occurs along the contact zone between pegmatite and epidiorite-hornblende schist of the Dhanjori Group (2.1–2.9 Ga). Host rock petrographic characteristics, along with the spatial distribution of the emerald, suggest a metasomatic origin for the emerald mineralization in the study area. The well-developed emerald crystals are found along the S2 schistosity plane, suggesting lithological and structural control on the mineralization. Electron microprobe data of the emerald indicates that the green hue is primarily due to the variable chromium content and Be could have been derived from the soda-granite of the Singhbhum Shear Zone. The average Cr2O3 and Cr concentration in the emerald is 0.038 wt% and 0.003 apfu, respectively. The ternary diagrams FeO–MgO–Cr2O3 and FeO–Cr2O3–V2O5 are plotted and superimposed on global emerald data, compiled from the literature, which shows the similarity of this deposit to other emerald deposits of the world. From the present study, it is inferred that the emerald deposits of Bahutiya and Gurabanda, Jharkhand, belong to the Type-IA category.
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2025,99(2):568-581, DOI: 10.1111/1755-6724.15285
Abstract:
Recent exploration has highlighted the critical role of strike-slip faults in shaping ultra-deep carbonate reservoirs in the Tarim Basin. This study integrates satellite imagery, UAV photogrammetry, outcrop surveys and microscopic analysis to investigate the architecture of these faults and their impact on reservoir petrophysical properties. The strike-slip faults exhibit cores consisting of calcite bands, fault breccias and fractures, while the damage zones are predominantly fractured. Thicker fault cores and fault zones are associated with more extensive reservoir development. Individual strike-slip fault zones are primarily characterized by two sets of fractures intersecting the fault at small angles. When two fault systems interact, the dominant pattern is two sets of fractures intersecting the main fault at small angles and one set at larger angles, facilitating the formation of large-scale reservoirs. We propose a model for the fault core, which primarily consists of a calcite band and fault breccias. These breccias are composed of original host rock, calcite cement and quartz, which exhibit poor physical properties, while fractures and vugs show favorable reservoir characteristics. This model offers valuable insights into the development of fault-controlled reservoirs, particularly in the Tarim Basin.
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HE Lijuan，YU Qiang，REN Zhanli，LI Rongxi，LEI Xianghe，SUN Xianyao，YANG Qike，WANG Tianzi，YUAN Ruize
2025,99(2):582-597, DOI: 10.1111/1755-6724.15278
Abstract:
The present-day pressure pattern is the ultimate result of the evolution of paleo-pressure, so understanding the variation of stress throughout geological history is of great significance for oil and gas accumulation. In this study, the fission track method was used to reconstruct the cooling history of sandstone samples from the Yanchang Fm. in the central–eastern Ordos Basin and the cause of the low-pressure anomaly in the Yanchang Fm. was analyzed. The max. burial depth pressure was reconstructed and the pressure evolution of the formation in the Futan 1 well was simulated, using Petromod 1D. The fission track data and Petromod 1D simulation results indicate that the Yanchang Fm. reached its max. burial depth and experienced a high paleo-pressure of 30.92 MPa at around 100 Ma. Since the Late Cretaceous, the formation pressure evolution in the study area can be divided into two stages. From 100 to 20 Ma, the formation slowly uplifted, with the pressure gradually decreasing. Since the Miocene (about 20 Ma), the pressure rapidly decreased to the current pressure of approximately 6.92 MPa. Based on the above research results, the influence of pore rebound and temperature decrease on formation pressure was quantitatively calculated. The results show that during the first stage, the pressure reduction caused by pore rebound and cooling was 3.86 MPa and 3.49 MPa, respectively, with a decrease of about 12.48% and 11.28%. During the second stage, the pressure reduction caused by pore rebound and cooling was 6.32 MPa and 9.60 MPa, respectively, with a decrease of about 20.43% and 31.04%. The formation of low pressure in the Yanchang Fm. in the central and eastern basin is mainly controlled by pore rebound and temperature reduction, caused by erosion after stratigraphic uplift. The decrease in temperature plays a decisive role in determining the formation process of the low-pressure oil reservoir.
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2025,99(2):598-610, DOI: 10.1111/1755-6724.15276
Abstract:
The SiO2'–CaO/(CaO + K2O) (S'CK) diagram is an empirically derived major element-based equivalent to the modal IUGS alkali feldspar–quartz–plagioclase classification scheme for granitoids. It employs the content of SiO2 and CaO/(CaO + K2O) ratio to approximate the IUGS classification diagram and a normative-based Q'–ANOR plot. Four trends have been superimposed onto the SiO2'–CaO/(CaO + K2O) diagram based on published datasets from the Peninsular Ranges (calcic: C), Tuolumne (calc–alkalic: CA), Sherman (alkali–calcic: AC), and Bjerkreim-Sokndal (alkalic: A) batholiths, which were employed to constrain the positions of the C–CA, CA–AC and AC–A suite boundaries on the SiO2 versus (Na2O + K2O – CaO) (or modified alkali–lime index, MALI) granitic classification diagram. A merit of the SiO2'–CaO/(CaO + K2O) plot is identifying rock types comprising a suite and their relative abundances. The distinguished projections of five typical granitoid assemblages, which are summarized by Bonin et al. (2020), demonstrate the ability of SiO2'–CaO/(CaO + K2O) diagram to decipher their petrogenesis. The SiO2' –CaO/(CaO + K2O) plots for the plutonic suites of 'known' tectonic settings can reveal their evolution paths and the lithological statistics. Accordingly, it is suggested that the SiO2'–CaO/(CaO + K2O) plot can distinguish the tectonic environments of plutonic suits by comparing the plutonic suites or batholiths of 'unknown' tectonic context to the published datasets from granitoid suites formed within 'known' tectonic settings. The modified SiO2'–CaO/(CaO + K2O) diagram links the bulk chemical composition of granitoid suites to the likely source, magmatic evolution, and tectonic setting; thus, it may be a useful tectono-magmatic classification scheme for granitoid suites.
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YUAN Lingling，CHAI Peng，HOU Zengqian，QUAN Haihui，SU Chongbin
2025,99(2):611-624, DOI: 10.1111/1755-6724.15277
Abstract:
Numerous intermediate to felsic igneous rocks are present in both subduction and collisional orogens. However, porphyry copper deposits (PCDs) are comparatively rare. The underlying factors that differentiate fertile magmas, which give rise to PCDs, from barren magmas in a specific geological setting are not well understood. In this study, three supervised machine learning algorithms: random forest (RF), logistic regression (LR) and support vector machine (SVM) were employed to classify metallogenic fertility in southeastern Tibet, Sanjiang orogenic belt, based on whole-rock trace element and Sr-Nd isotopic ratios. The performance of the RF model is better than LR and SVM models. Feature importance analysis of the models reveals that the concentration of Y, Eu, and Th, along with Sr-Nd isotope compositions are crucial variables in distinguishing fertile and barren samples. However, when the optimized models were applied to predict the datasets of Miocene Gangdese porphyry copper belt and Jurassic Gangdese arc representing collision and subduction settings respectively, a marked decline in metrics occurred in all three models, particularly on the subduction dataset. This substantial decrease indicates the compositional characteristics of intrusions across different tectonic settings could be diverse in a multidimensional space, highlighting the complex interplay of geological factors influencing PCD’s formation.
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2025,99(2):626-626, DOI:
Abstract:
