Abstract:Hupehsuchus nanchangensis is the most representative species of the Nanzhang- Yuanan Fauna and one of the oldest known marine reptiles. However, information regarding the key cranial features of this species remains scarce. To address this gap, a recently collected fossil specimen was carefully repaired and studied using comparative anatomical methods. This study revises the following cranial diagnoses of this species: ① a narrow bony space develops along the midline of the skull develops along the two branches of the upper jaws; ② the premaxillae contact each other at their anterior ends, while the nasals only contact at their posterior ends; ③ a groove is present on the premaxilla, aligned with a similar groove on the maxilla; ④ the skull roof is flat and lacks a sagittal crest; ⑤ the parietal bone is larger than the frontal, and the pineal foramen is located in the anteromedial part of the parietal; ⑥ the upper temporal fenestra is formed by parietal, postfrontal, postorbital, and squamosal bones, excluding supratemporal; ⑦ the jugal is a triradiate bone with a thin, elongated anterior process and a short ventral process; ⑧ the supraoccipital is large and nearly circular; and ⑨ the exoccipital has clearly visible nerve openings. Comparative analysis reveals that Hupehsuchus nanchangensis, Nanchangosaurus, and Eretmorhipis all possess bony spaces formed between the upper jaws, which may represent a homologous character of Hupehsuchia. In Hupehsuchus nanchangensis, the supratemporal does not participate in the formation of the upper temporal fenestra. In addition, this species retains morphological vestiges of the jugal' s ventral process, and its inferior temporal fenestra is not fully reduced, resembling the condition in the oldest diapsid reptiles but different from the advanced ichthyosauromorphs. It is speculated that during the evolution of ichthyosauromorphs, the supratemporal gradually shifted anteriorly and became incorporated into the upper temporal fenestra, while the inferior temporal fenestra gradually closed. The new material also shows that the external naris of Hupehsuchus nanchangensis faces dorsally, and its bite force was relatively weak. These features suggest that this species had a unique feeding mechanism distinct from other ichthyosauromorphs.

Abstract:Although the Mianyang- Changning intracratonic sag is widely recognized as a key petroleum accumulation site, its spatio- temporal distribution and formation mechanisms are still controversial. To address this, systematic stratigraphic and lithofacies investigations were carried out on the Sinian- Cambrian successions in the Guangyuan- Ningqiang area, located at the northeastern margin of the Mianyang- Changning intracratonic sag. Lithofacies indicators and biostratigraphic data suggest that the lower Beiwan Member or upper Algal Dolomite Member are commonly overlain by the Kuanchuanpu Formation, indicating that the Gaojiashan and Beiwan Members are pervasively missing in the Kuanchuanpu, Shujiaba, and Caojiaba- Dongshanzi areas. This indicates that the strata missing of the upper Dengying Formation at the eastern margin of the Mianyang- Changning intracratonic sag extends from the central Sichuan basin and the northern slope of the central Sichuan paleouplift to the Guangyuan- Ningqiang area. A sharp facies transition from tidal flat- lagoonal microbial dolomite and dolomudstone in the study area to slope- basinal chert in the Datan- Yangmu area indicates the influence of extensional faulting. Similar abrupt facies shifts are observed at the southern margin of the middle Yangtze platform and the eastern margin of the upper Yangtze platform, reflecting an extensional tectonic regime characterized by fault- bounded carbonate platforms. The spatial extent of several kilometers, erosion thickness of hundreds of meters, and the depositional break of up to 20 Ma suggest that the Mianyang- Changning intracratonic sag resulted from differential subsidence/uplift rather than karstic morphology. The linear distribution of strata missing area at the eastern margin of the Mianyang- Changning intracratonic sag is interpreted as the result of relative uplift at a tilted block. The climax of extensional faulting occurred at the Sinian- Cambrian transition, causing the strata missing from the upper Dengying Formation to the lowermost Kuanchuanpu Formation.

Abstract:Pollen fossils, stable isotopes, framboid pyrites, and major elements were analyzed in the Yanchang Formation from core ZH2 to investigate the response of the Carnian pluvial event in the southern Ordos basin. Two pollen fossil assemblages were identified from bottom to top: (Ⅰ) the Punctatisporites- Verrucosisporites- Osmundacidites assemblage and (Ⅱ) the Asseretospora- Apiculatisporis assemblage. The geological dates of these assemblages correspond to the Middle Triassic (Ladinian) and the Late Triassic (Carnian),respectively. The Zhangjiatan shale, located in the lower part of pollen assemblage Ⅱ, exhibits enriched total organic carbon (TOC) content and a negative organic carbon isotope shift of 4. 88‰. Concurrently, the framboid pyrite index indicates that this layer formed in anoxic conditions. Additionally, high values of Al2O 3/MgO and the chemical index of alteration (CIA) indicate a high- temperature, humid climate with enhanced chemical weathering. These characteristics collectively demonstrate that the Carnian pluvial event had a significant impact on the Ordos basin. Further analysis shows that these indicators can be subdivided into four distinct intervals within the Zhangjiatan shale, each marked by high temperatures, humidity, anoxia, and organic carbon enrichment. These intervals represent four climatic fluctuations associated with the Carnian pluvial event in the Ordos basin, designated as CPEⅠ, CPEⅡ, CPEⅢ, and CPEⅣ.

Abstract:The continuous subduction of paleo- oceans has resulted in the presence of numerous microplates in Southeast Asia, characterized by complex origins and tectonic evolution. This complexity poses significant challenges for paleogeographic reconstruction, particularly concerning the Northeast Borneo terrane, whose tectonic attributes and pre- Cenozoic paleogeography remain highly controversial. The Baliojong Ocean Plate stratigraphy outcropping in Northeast Borneo serves as a valuable record of paleo- oceanic history, spanning from crustal spreading to subduction and extinction. In this study, we conducted detailed provenance and geochronological investigations on two turbidite sections in the western part of the Baliojong Ocean Plate stratigraphy. By integrating whole- rock geochemistry, mineralogy, and zircon U- Pb geochronology- geochemistry- morphology, we determined the depositional ages and compositions, thereby revealing the subduction history and paleogeography of the overlying plates. Our results demonstrate significant differences between the two sections in terms of individual provenance and geochronological proxies. Turbidites in the eastern section (BF2) exhibit younger sedimentary ages, higher compositional maturity and detrital content, mafic- dominated source composition, and a greater abundance of larger- sized zircon grains of Caledonian and Indosinian ages compared to those in the western section (BF5). These lines of evidence clearly indicate that the two turbidite sequences are products of distinct accretionary periods. Combining our newly obtained maximum depositional age proxies based on detrital geochronology with published ages of radiolarian cherts and basalts, we interpret the deposition of the turbidite sequences to have occurred in the Late Cretaceous (~87 Ma and ~93 Ma). Comparison of the zircon U- Pb age signatures of the Baliojong turbidites with those of potential source areas in Borneo and surrounding plates suggests a provenance linkage to the zone encompassing the southern Indochina margin- East Malaya- Northwest Borneo. We interpret the location of the subduction zone, where the Baliojong Ocean Plate stratigraphy formed, to be closer to Sundaland than South China. The Late Cretaceous paleogeography of Northeast Borneo revealed in this study holds significant implications for reconstructing the Mesozoic subduction system in the South China Sea- Southeast Asia region.

Abstract:Numerous significant earthquakes have occurred in the Tibetan Plateau since the recent decades years, attracting considerable attention from scholars both domestically and internationally. These major earthquakes often occur along enormous fault zones, which not only exhibit intense activity in the late Quaternary period but also possess structural conditions necessary for the development and occurrence of strong earthquakes. The Karakorum fault stands out as a large- scale dextral strike- slip fault in the western part of the Tibetan Plateau. The part south of the Lungmu Co fault more pronounced activity and has experienced the Pulan M S7. 0 earthquake in 1883. Understanding the most recent deformation behavior of this fault and analyzing its seismogenic characteristics are crucial in identifying the segmented activity patterns and surface rupture features of the fault zone. Based on high resolution remote sensing image interpretation and field geological survey, the late Quaternary segmented activity of the southern section of the Karakorum fault and the Chaxikang surface rupture zone have been meticulously investigated. The findings reveal that the southern section of the fault zone can be further divided into three primary segments: Ladakh- Chaxikang, Kunsha- Bar and Menshi- Gongzhu Co segment. These segments are characterized by dextral strike- slip, dextral strike- slip normal faulting and dextral strike- slip with a horsetail normal fault, respectively. Measurements taken from the surface rupture zone indicate a minimum horizontal displacement of 8~9 m. Considering the approximately 200 km length of the surface rupture, it is estimated that the magnitude of the earthquake could be ~7. 5. The Karakorum fault zone, which controls the material extrusion in the western plateau, gradually transforms from a rigid block migration mode in the northwest section to a more dispersed arc- shaped normal fault and strike slip deformation in the southeast section.

Abstract:To gain a comprehensive understanding of the electrical structure and geological structural characteristics of the Jingerquan region in eastern Tianshan, and to provide electrical evidence for its metallogenic mechanism, a magnetotelluric sounding profile was completed in the area. By utilizing three- dimensional inversion, a reliable electrical structure model was obtained. The results revealed the following insights: ① the shallow part of the Kangur- Huangshan ductile shear zone exhibits a thin layer of high conductivity. This suggests that the shallow surface rock layer may have undergone significant ductile shear deformation, leading to the presence of fractured and loose rock, potentially accompanied by fluids; ② the Yamansu fault serves as a channel for fluid transport to greater depths, causing the fractures below it to exhibit high conductivity anomalies; ③ the mineralization model of the Hulu copper- nickel sulfide deposit is consistent with the magma channel mineralization model. The Kangur Fault serves as a pathway for the upward intrusion of mantle- derived magma. During this process, the magma carries copper- nickel sulfides, which subsequently undergo gravitational subsidence and aggregate mineralization at bends in the channel, magma chambers, or dilation sites. Additionally, it is speculated that there may be sulfide- rich basic rocks at a depth of 2 km, suggesting the potential for Cu- Ni metallogenic at that depth.

Abstract:As an essential component of the continental crust, the products and magmatic systems of silicic volcanic activity recorded the vital information on the continental crust differentiation. Intensive Cretaceous volcanism was widespread along the coastal area of SE China, dominated by rhyodacites and rhyolites, offering a unique opportunity to unravel the growth and evolution of transcrustal magmatic systems. Here we present systematic zircon Hf isotopic data integrated with previous researches for the Changyu caldera in eastern Zhejiang Province, in order to constrain the magma sources and evolution of the magmatic system. The different eruption stages of the caldera, including caldera- forming eruptions, post- caldera eruptions and the rhyolite domes show consistent zircon Hf isotopic compositions with εHf(t) values of 7.4 to0.2 and TDMC Hf model ages of 1.45 Ga to 1.04 Ga, suggesting the genetic link of the volcanic rocks of different eruption stages and that the magmas were mainly formed by the mixing of depleted mantle- derived magma and magma derived from ancient crust of the Cathaysia block. The compiled zircon Hf isotope data of the Late Jurassic to Cretaceous volcanic rocks from the coastal SE China reveal that their εHf(t) values are typically located far below the depleted- mantle evolution trend with a particularly wide range, and their TDMC Hf model ages cluster mainly between 1.8 and 1.0 Ga almost without Archean ages. This implies that the ancient crustal basements of the Cathaysia block should also be prevalent beneath the volcanic field east of the Zhenghe- Dapu fault, besides the sporadic outcrops of the Precambrian basement rock, and that the ancient crust materials were involved to varying degrees in the origin of volcanic magmas along the coastal SE China. Furthermore, the generation of high- silica rhyolitic magmas from the Changyu caldera and other Cretaceous calderas in the coastal SE China reflects the long- term evolution of the transcrustal magmatic system as well as crystal- melt segregation processes. Juvenile mantle- derived magmas not only contribute to the genesis of silicic magmas and the growth of continental crust, but also supply the necessary magma and heat flux for the transcrustal magmatic system of the large- scale silicic volcanism. The internal and external structures of calderas, the comprehensive mapping on genetic types, spatiotemporal distributions, as well as the volcanic eruption history are the crucial foundations and important contents of future studies on the transcrustal magmatic systems of the intensive Cretaceous volcanism in the coastal area of SE China.

Abstract:Early Ordovician mafic dykes exposed in thenorth Kunlun are of great significance for understanding the subduction processes and dynamic background of the paleo- active continental margin. In this paper, we present detailed petrology, zircon U- Pb chronology, whole- rock geochemistry and Sr- Nd isotopes of the mafic dykes. Zircon U- Pb dating results show that the zircon U- Pb ages of these dykes range from 486 to 483 Ma, suggesting an Early Ordovician age. Whole- rock geochemical results show that the mafic dykes have low SiO2 (50. 06%~51. 68%), medium MgO (5. 08%~6. 77%) and TiO2 (0. 99%~1. 20%) content, and belong to the tholeiitic basalt series. Regarding trace and rare earth elements, the rocks are enriched in large- ion lithophile elements (e. g. , Rb, Sr, Ba, Th, K) and depleted in high- field- strength elements (e. g. , Nb, Ta, Ti). The chondrite- normalized REE diagrams are featured by weak enrichment of LREE and depletion of HREE, with weak Eu anomaly. In addition, the dykes show high (87Sr/86Sr)i (0. 7126~0. 7133) and relatively low εNd(t) isotopic composition (9. 80~4. 31) of the enriched lithospheric mantle. The petrogenesis research indicates that the basic magma originated from the enriched lithospheric mantle, was metamorphosed by fluids in the subduction zone, and subsequently experienced fractional crystallization mainly of olivine and clinopyroxene during the diagenetic processes. Based on the regional geological data, we argue that the Kunzhong Ocean subducted northward in early stages of the Early Paleozoic and formed a magmatic arc system. It may have experienced the retreat of the subducting oceanic slab at 486 Ma, leading to an extensional tectonic setting in the upper plate of the subduction zone and then generation of mafic dykes.

Abstract:Georgechaoite and bobtraillite, rare zirconosilicates, were discovered as secondary alteration products of eudialyte within the Saima alkaline complex in Liaoning Province, China. An integrated study encompassing petrography, mineralogy, geochemistry, and isotopic geochronology was conducted to revealtheir occurrence, crystal structure, and chemical composition. This investigation aimed to constrain the ages of magmatic enrichment and hydrothermal alteration of Zr- REE- bearing minerals, ultimately exploring the relationship between post- magmatic fluid events and the mobilization- precipitation of ore- forming elements. Georgechaoite, an early alteration mineral, commonly occurs as anhedral crystals associated with secondary gaidonnayite, natrolite, britholite- (Ce), and other alteration minerals. It crystallizes in the orthorhombic system with unit cell parameters: a=1. 18325(5) nm, b=1. 29141(3) nm, c=0. 67292 (1) nm, V=1. 02825(4) nm3, and an empirical formula of (Na0. 97K0. 78Ca0. 06Pb0. 01Sr0. 01)Σ1. 83(Zr0. 98Ti0. 01Hf0. 01)Σ1. 00Si3. 02O9·2H2O. Bobtraillite,a later alteration mineral, posterior to georgechaoite, exhibits anhedral crystals or aggregates in close association with secondary natrolite, zircon, strontianite, calcite, britholite- (Ce), and other alteration minerals in the pseudomorph after eudialyte, with few remnants of eudialyte, gaidonnayite, or georgechaoite. It crystallizes in the trigonal system with unit cell parameters: a=1. 96634(3) nm, c=0. 99581(3) nm, V=3. 33445(1) nm3, and an empirical formula of (Na7. 10Ca0. 99K0. 01□3. 90)Σ12. 00(Sr10. 42Ca1. 56Ba0. 01Pb0. 01)Σ12. 00(Zr12. 85Ti0. 49Hf0. 13Al0. 08Nb0. 06□0. 39)Σ14. 00Si42. 01B5. 99O132(OH)12·12H2 O. Geochronological data indicate that the primary eudialyte alteration occurred around 218±5 Ma. Georgechaoite formation is attributed to alkali- rich metasomatic fluids derived from the Saima alkaline magmas. In contrast, the age of bobtraillite formation is 107±5 Ma, probably related to external carbonate fluids mobilized by the subduction of the ancient Pacific plate. Hydrothermal alteration led to the release of a significant portion of REEs from the precursor eudialyte into the fluid system, with only the minority being preserved in secondary minerals (e.g. , georgechaoite and bobtraillite). The discovery and characterization of georgechaoite and bobtraillite provide valuable insights into the nature and ages of post- magmatic fluid eventsin the Saima alkaline complex. These findings have significant implications for understanding the remobilization- precipitation mechanisms of critical metals (e.g. , Zr and REEs) in hydrothermal environments.

Abstract:Mesozoic intermediate- acid intrusive rocks are widespread in the Tongling ore concentration area of Anhui Province and are closely related to polymetallic- copper mineralization. Although numerous studies have investigated the genesis of these intrusions, controversies remain. This study focuses on Tongguanshan and Dongguashan quartz diorite and Fenghuangshan and Hucun granodiorite to further explore their genetic mechanisms. We conducted a comprehensive geochemical analysis, including major and trace element compositions, Sr- Nd isotopic ratios, and zircon and apatite geochemistry. Integrating these data with previous research, we propose a refined model for the origin of these intrusive rocks. Our findings indicate that the Mesozoic intermediate- acid intrusive rocks share similar major and trace element compositions, classifying them as high- K calc- alkaline rocks with characteristics of both arc magmatic and adakitic- like rocks. They also exhibit enriched Sr- Nd isotopic compositions. These geochemical characteristics, coupled with petrological observations of mafic microgranular enclaves (MMEs) and antiband structures of amphibole and plagioclase, indicate that their parental magma originated from the mixing of mafic and felsic magmas. Our new analytical results provide further insights into the petrogenesis of these intrusions. Inherited zircon U- Pb ages predominantly cluster within two ranges: 1.0~0.8 Ga and 2.4~2.0 Ga. Corresponding εHf(t) values range from 20.5 to 5.1, indicating two- stage Hf model ages between 1.5 and 2.9 Ga. Zircon δ18O values fall between 5.93 ‰ and 8.85 ‰. Apatite geochemistry reveals high Cl contents (average 0.3%) with relatively high Cl/F ratios (0.052~0.244), high REE contents (1714×10-6~5903×10-6), and negative δEu values (0.26~0.68). Based on combined geochemical characteristics of whole rocks, zircon, and apatite, and considering regional geological tectonic evolution, we challenge existing views on the genesis of these intrusions and propose a new model. We suggest that the Mesozoic intermediate- acid intrusive rocks in the Tongling ore concentration area originated from a mixture of crust- derived and mantle- derived magmas. Specifically, this involved the mixing of enriched lithospheric mantle- derived magma with Neoproterozoic juvenile arc crustal- derived magma. A minor contribution from ancient crustal materials, dating back to the Paleo- Proterozoic to Meso- Proterozoic, was also incorporated during magma ascent. The enriched lithospheric mantle source magma was derived from the subducted oceanic crust or the fluid metasomatic overlying lithospheric mantle when the Cathaysia oceanic slab subducted beneath the Yangtze craton in the Neoproterozoic era, rather than the Mesozoic Paleo- Pacific slab subducting beneath the South China plate. The rollback of the Mesozoic Paleo- Pacific slab triggered the extension and thickening of the ancient orogenic belt, leading to lithospheric mantle thinning and melting.

Abstract:Several vein- like silver polymetallic deposits are developed in Luoning County, western Henan Province, China. Among these, the Shagou deposit, characterized by significant Ag- Pb- Zn mineralization, commonly contains authigenic quartz grains coeval with sulfides.These quartz grains provide valuable insights into the physicochemical conditions prevailing during different mineralization stages and the precipitation mechanisms of metal minerals from ore- forming fluids. This study presents a detailed mineralogical investigation of quartz in the Shagou deposit, utilizing cathodoluminescence (CL) imaging, fluid inclusion microcalorimetry, and individual fluid inclusion composition analysis. These techniques were applied in conjunction with detailed field geological investigations. The mineralization process of the Shagou deposit comprises three stages: a quartz- siderite- pyrite stage, a quartz- dolomite- polymetallic sulfide stage, and a quartz- calcite stage. In the quartz- dolomite- polymetallic sulfide stage, three generations of quartz were identified: ① Q1, located in the core of quartz grains, exhibits uniform bright CL intensity with undeveloped growth zonings; ② Q2, found in the mantle of quartz grains and coeval with sulfides, is characterized by dark CL intensity and chaotic growth zonings; ③ Q3, situated at the edge of quartz grains, displays bright CL intensity with well- defined growth rings. Compositional analysis of quartz from various generations revealed a strong positive correlation between Al and Li content (R2 = 0.97) across all stages. This correlation is closely linked to CL brightness, indicating that Al3+ and Li+ substitute for Si4+ within the quartz structure. Ti content in Q1 and Q2 ranges from 0.722×10-6 to 3.62×10-6 and 0.387×10-6 to 1.12×10-6, respectively, while Al content ranges from 81.9×10-6 to 2436×10-6 and 3.67×10-6 to 132×10-6, indicating a medium- low temperature hydrothermal environment for mineralization, with decreasing temperature and increasing pH as the primary factors triggering mineral precipitation. LA- ICP- MS analysis of single fluid inclusions showed enrichment in alkali metals with high Rb/Na and Cs/Na ratios. This strongly suggests a magmatic origin for the mineralizing fluid, classifying the Shagou deposit as a magmatic- hydrothermal mineralization system.

Abstract:The Ordos basin has long been considered a stable block with few faults within its interior. However, recent advancements in 3D seismic technology have revealed a significant number of small- scale faults within the basin, challenging previous assumptions about its structural characteristics and influencing the direction of the oil and gas exploration. Despite these discoveries, the geometry, kinematics characteristics, and genetic mechanism of these faults remain unresolved, and the factors controlling the accumulation of oil and gas in relation to these faults are still unclear. In this study, we aim to compare the characteristics of strike- slip faults developed in different units of the Ordos basin and analyze their impact on hydrocarbon accumulation. The observed faults in the Ordos basin exhibits various trends, including ENE, NW, N- S, and E- W. These faults share common features such as sub- vertical dip angle, small slip distance, and concealment. Furthermore, all of these faults show the nature of strike- slip characteristics. However, the dominant strike direction of faults varies across different regions of the basin, which is nearly E- W- trending in the north, ENE- trending in the south, the NW- trending in the southwest, and multi- direction strikes of faults were exhibited in the interior of the basin. The formation and evolution of these intrabasinal faults are controlled by the tectonic stress surrounding the basin, with faults in periphery forming under similar stress conditions and the stress strength being weaker within the interior of the basin. Due to the discontinuity structure style of faults in the Ordos basin, the upper and lower petroleum systems are independent of each other. The Mesozoic internal primarily consists of fault- fracture volume in clastic reservoirs, while the Lower Paleozoic interval comprises fault- karst volume in carbonate reservoirs. The assemblage of faults and associated fractures within the interior of the Ordos basin represents unique reservoir sweet spots.

Abstract:The complexity of shale oil reservoirs within alkaline lacustrine basins complicates the accurate identification of desserts. This study focuses on the Fengcheng Formation in Mahu sag of China' s Junggar basin. We carried out lithofacies typing, evaluated full- aperture reservoir space systems using high- pressure mercury injection and low- temperature nitrogen adsorption experiments, and analyzed sedimentation and diagenesis to understand reservoir formation mechanisms. Our results reveal four distinct lithofacies types in the Fengcheng Formation: stratified dolomitic siltstone, lamellar felsic shale, lamellar lime- dolomite shale, and stratified felsic- lime dolomite. Stratified dolomitic siltstone exhibits the largest full- aperture reservoir space (1. 81 cm3/g) and the highest macropore volume (0. 51 cm3/g). Its porosity is attributed to primary intercrystalline pores within microcrystalline quartz, dissolution pores in feldspar and alkaline minerals, and a significant number of dissolution and structural fractures, resulting in excellent pore- fracture connectivity among these four lithofacies types. Lamellar felsic shale, with a full- aperture reservoir space of 1. 32 cm3/g and a macropore volume of 0. 34 cm3/g, primarily forms spherical dissolution pores in talc and mica, as well as organic pores. Locally dissolved fractures contribute to moderate pore- fracture connectivity. Both Lamellar lime- dolomite shale and stratified felsic- lime dolomite exhibit intragranular pores, residual intergranular pores, and small- diameter dissolution pores. The former has a total pore volume of 0. 49 cm3/g and a macropore volume of 0. 13 cm3/g, while the latter has values of 0. 41 cm3/g and 0. 08 cm3/g, respectively. Both two types of lithofacies display poor pore- fracture connectivity. The average pore diameter in these reservoirs positively correlates with felsic mineral content and negatively correlates with dolomite content. Consequently, stratified dolomitic siltstone is identified as the dominant lithofacies. The formation of shale oil reservoirs in this setting is controlled by sedimentation and diagenesis. Fine- grained gravity flow sedimentation delivers highly porous silty sediments into the deep lake environment. Subsequent dissolution, recrystallization of silicon within the alkaline lake, and fracture formation create the excellent storage space observed in intercrystalline pore and dissolved fracture. These findings provide valuable insights for evaluating shale oil desserts in similar geological settings.

Abstract:To understand the activity range and characteristics of hydrothermal fluids in the Songliao basin and analyze their influence on the porosity- permeability of the shale reservoir,as well as their relationship with present- day overpressure, this study focuses on the Qingshankou Formation shale in the Gulongsag. Our research combines microscopic and scanning electron microscope observations, electron probe measurement, XRD analyses of clay minerals, homogenization temperature and Laser Raman spectroscopy of fluid inclusions, vitrinitereflectance, rock pyrolysis, and carbon and oxygen isotope analysis of carbonate cement. We integrate these findings with previous research results. Our results show that hydrothermal fluids, associated with tectonothermal events and magmatic activity, have significantly impacted the shale reservoir. This is evidenced by anomalies invitrinite reflectance and rock pyrolysis parameters, accelerated transformation rates of authigenic clay minerals, and a higher fluid inclusion homogenization temperature than expected based on maximum buried depth. The δ18O values of carbonate cement and δ34S values of authigenic pyrite are consistent with those of magmatic rocks,further supporting the influence of hydrothermal fluids. We identified a typical hydrothermal mineral assemblage in the shale, suggesting that deep hydrothermal fluid activity primarily occurred below 2000 m. The zones of high porosity and permeability in the Qingshankou shale coincide with zones of hydrothermal fluid activity and overpressure development. The intrusion of hydrothermal fluids, rich in inorganic CO2, inhibited carbonate cementationto some extent and promoted the dissolution of soluble minerals, leading to the formation of secondary pores and improving the physical properties of the shale reservoirs. Meanwhile, hydrothermal activity accelerated the thermal maturation of organic matter,enhancing hydrocarbon generation from the source rocks and increasing its hydrocarbon production capacity. We propose that the abnormal pressure in the Gulong sag is mainly due to hydrocarbon- generating expansion, with hydrothermal activity and its associated heating effect also contributing to the maintenance of overpressure.

Abstract:Optimizing the production and reinjection parameters of a “doublet” system is of significant importance for the sustainable development and utilization of geothermal resources in sandstone thermal reservoirs. This system, consisting of a closed loop with one production well and one reinjection well, plays a vital role in the temperature recovery of reinjected cooled geothermal water. In this research paper, we establish a hydro- thermal coupling numerical model for the “doublet” system based on the long- term hydrodynamic and geo- temperature monitoring data from the production and reinjection wells at the Guantao Formation thermal reservoir. Our study focuses on understanding the evolution and trend of the temperature field in the thermal reservoir caused by reinjected cooled geothermal water. Additionally, we aim to optimize the key parameters of both the existing and planned “doublet” systems. Furthermore, we investigate the heat sources contributing to the temperature recovery of the reinjected cooled geothermal water and provide a quantitative calculation. The findings reveal that the basal conglomerate at the bottom of the Guantao Formation reservoir, with its high permeability, exhibits the fastest migration rate for reinjected cooled geothermal water. To ensure the absence of thermal breakthrough in the production well of a typical “doublet” system within 100 years of operation, the production and reinjection flow rate Q should not exceed 30 m3/h. When the production and reinjection flow rate Q of the proposed “doublet” system is designed with a conventional value of 72 m3/h, the reasonable distance R between the production and reinjection wells should not be less than 300 m. The thermal breakthrough time t in the production well increases as a power function with the increase in the distance R, as described by the correlation equation tQ=aR2. 4. Examining the heat sources contributing to the temperature recovery of reinjection cooled geothermal water, the analysis indicates that the convection heat between the reinjection cooled geothermal water and its peripheral hot geothermal water in the same layer is the source of heat recovery with the largest proportion, accounting for more than 70% at the beginning of reinjection and remaining at 36.0% after 100 years of reinjection. The proportion of conduction heat absorbed by cold water from the roof and floor of the reservoir increases from nearly 0% to 30. 7% (roof: 11. 5%, floor: 19. 2%) in 100 years of reinjection. The proportion of conduction heat in the same layer absorbed by the reinjected cold water from the peripheral heat reservoir media increases rapidly from nearly 0% to 13. 5% and then stabilizes. The proportion of heat absorbed by the cooled geothermal water from the internal reservoir medium gradually decreased from 25.4% at the beginning of reinjection to 19. 8% at 100 years of reinjection.

Abstract:The coastal area of Guangdong Province exhibits a significant abundance of hot spring resources, making it an important geothermal resource region characterized by medium- low temperature hydrothermal activity. Through field investigation, the crust- mantle temperature structure of the hot spring geothermal system in this area was determined using magnetic, gravity, and seismic methods. The results indicate a Curie temperature of 550℃ and a Moho surface temperature ranging from 635℃ to 812℃. The mantle exhibits weak upwelling, and the thermal background displays a slight elevation. Interestingly, two distinct dVs negative regions were identified at a depth of 20 km beneath the hot spring geothermal anomaly areas located in both western and eastern Guangdong province. These anomalies are hypothesized to represent high- temperature hydrothermal activity zones in the lower crust. Genetic analysis of the hot spring geothermal system shows that the NE deep- large fault is an important thermal conduction structure. This fault not only acts as a preferential channel for the upward transfer of heat from deep sources but also facilitates heat exchange between groundwater and the surrounding rock. The heat source for this geothermal system comprises three distinct components: a deep mantle heat source, a lower crustal heat source originating from the high- temperature hydrothermal active areas, and a near- surface strata heat source with a high heat generation rate. The primary water source is atmospheric precipitation, which infiltrates underground through fault fractures and weathered granite, subsequently being heated by the heat sources. This heated groundwater accumulates near the surface of thermal conduction structure, forming a subsurface heat reservoir. Finally, it emerges as hot springs in structurally favorable locations. The average depth of hot water circulation within the hot spring geothermal system in eastern Guangdong is greater than that observed in western Guangdong.

Abstract:The Sela ancient landslide, located in the Jinshajiang suture belt, exhibits obvious signs of reactivation deformation, posing a significant risk of large- scale instability, potentially leading to a landslide, river blockage, and subsequent flood disaster chain. This study uses optical remote sensing dynamic monitoring, engineering geological surveys, and numerical simulation to analyze the reactivation deformation characteristics, simulate the stability, and predict the potential river- blocking outburst of the Sela ancient landslide. The results indicate that the Sela ancient landslide is a huge landslide with an estimated volume of 6300×104 to 9500×104 m3. The sliding mass comprises broken stone and soil, while the sliding bed consists of mica quartz schist belonging to the Permian to Lower Triassic Gangtuo Rock Group. The landslide displays obvious signs of reactivation deformation, currently in a stage of creep deformation. Continuous deformation has been observed from 2018 to 2023, mainly concentrated at the front edge of the slope. The Sela ancient landslide reactivates and slides along the pre- existing sliding surface, exhibiting traction- type progressive failure mechanisms. The stability analysis identified four potential instability modes. Under natural conditions, zone Ⅲ- 2 is unstable, with a landslide duration of about 35 seconds. The maximum landslide speed reaches 30 m/s. The resulting barrier dam would be approximately 97 m high, creating a barrier lake with a capacity of about 1.56×108 m3. The failure of this dam would generate a maximum flood flow of approximately 3650 m3/s and a maximum flood peak height of approximately 14 m at the Lava Power Station dam site. Similarly, under natural conditions, if zones Ⅲ- 3 zone or Ⅲ- 4 become unstable, the barrier dam height would be around 88 to 90 m, with a barrier lake capacity of approximately 1.22×108 m3. The dam failure would result in a maximum flood flow of approximately 2900 m3/s and a maximum flood peak height of approximately 12 m at the Lava Power Station dam site. Under earthquake conditions, simultaneous instability of zones Ⅱ and Ⅲ is predicted. This scenario would result in a barrier dam approximately 152 m high, creating a barrier lake with a capacity of about 5.88×108 m3. Dam failure would generate a maximum flood flow of approximately 19270 m3/s and a maximum flood peak height of approximately 44 m at the Lava Power Station dam site. To mitigate the potential casualties and property losses associated with this chain disaster, continuous monitoring of the Sela landslide using an integrated space- air- ground approach is strongly recommended.

Abstract:Changbaishan Mountain, one of the most well- preserved polygenetic composite active volcanoes, boasts a diverse range of surface cover types, making it an ideal location for studying volcanic eruption landforms. The clear interpretation labels in remote sensing imagery make this region a valuable resource for large- scale volcanic landform classification using deep learning methods. This paper introduces the volcanic eruption landform scene dataset (VELSD1. 0), derived from Sentinel- 2 remote sensing imagery of Changbaishan Mountain, China. The dataset was developed in conjunction with geological data and field investigations. In the dataset, VELSD1. 0 comprises ten surface cover types: high vegetation coverage, middle vegetation coverage, low vegetation coverage, exposed soil, basaltic rocks, trachytic rocks, mixed rocks of trachyte and pumice, water, shadow, and artificial landscape. The dataset includes three constituent elements: remote sensing images, labeled data, and an interpreted label and explanatory file. Covering an area of 2500 km2, the dataset contains approximately 40,000 sample images of volcanic eruption landform. Each sample image measures 25 pixels×25 pixels with the spatial resolution of 10 m. To validate and analyze VELSD1. 0, we employed both classical convolutional neural networks (e. g. , GoogLeNet, ResNet) and transformer- based architectures (e. g. , Vision Transformer, Swin Transformer). Experimental results demonstrate the dataset' s strong applicability and transferability for deep learning models, achieving an overall classification accuracy (OA) of 82. 93%, a Kappa coefficient (KC) of 75. 64%, and a mean average precision (mAP) of 84. 22%. VELSD1. 0 effectively supports deep learning classification of other volcanic eruption landforms from remote sensing imagery, contributing to the informatization and intellectualization of remote sensing surveys for volcanic landforms.

Abstract:The development of effective hydrocarbon reservoirs in clastic sedimentary rocks subjected to deep burial conditions is a crucial area of investigation in reservoir research and hydrocarbon exploration. With the continuous development of exploration practices, geological understanding, and engineering technologies, traditional interpretations of deep reservoir formation are continually refined. Current exploration practices have confirmed the existence of effective clastic rock reservoirs at depths ranging from 6000 m to 8000 m. Through a comprehensive review of the literature on deep- buried reservoir formation mechanisms, combined with multi- scale observations of typical deep reservoirs in the four major basins of the central and western regions, the effect of original sedimentation conditions and various diagenetic processes on reservoir formation has been clarified. Our findings show that under deep and ultra- deep conditions, several key factors contribute to the preservation of primary pores and the formation of dissolution pores in clastic rocks. These factors include favorable sedimentary hydrodynamic conditions, multi- stage hydrocarbon charging, overpressure conditions, and the inhibitory effect of low geothermal fields on diagenetic evolution. Late structural transformation can enhance reservoir permeability through the formation of fractures. Therefore, ultra- deep clastic rocks possess significant exploration potential. Favorable zones of reservoir development in clastic rocks, governed by the interplay of sedimentation, diagenesis, and tectonic activity, represent promising exploration targets.

Abstract:Karst bauxite is the most important source of bauxite in China, accounting for more than 90% of the total resources, mainly distributed in the North China Craton and the southwest margin of the South China Block. In recent years, as a kind of strategic scarce mineral resource, the prospecting prediction of bauxite has become extremely urgent. This paper systematically summarizes the results of karst bauxite prospecting prediction and explores the optimal combination of prospecting prediction methods, so as to summarize the prospecting experience. By combing the examples and methods of geology, geophysics, geochemistry, remote sensing and artificial intelligence of geological big data to review the research results of karst bauxite prospecting and prediction in China, it is considered that geology and geophysics are still the most major methods for Chinese karstic bauxite prospecting prediction at present. In addition, the limitation of geochemical and remote sensing methods in searching for paleo- karst bauxite and their causes are analyzed, and the far- reaching significance of intelligent prospecting with geological big data is pointed out in the future.

Abstract:Enhanced basalt weathering has the potential to release and accumulate heavy metals in soil, while the weathering products of basalt can have a passivating effect on these metals. Therefore, investigating the bioavailability of heavy metals in soil during the enhanced basalt weathering process is of great significance for the practical application of enhanced basalt weathering carbon sequestration technology. This study used the Tessier method, SEM, EDS, and other characterization methods to investigate the effects of enhanced basalt weathering on soil heavy metals. Our results showed that basalt weathering increased soil pH, promoting the passivation of heavy metals in soil. Most of the Cr and Ni leached from basalt were immobilized in the residual fraction by basalt weathering products and soil clay minerals. Only a small amount of Cr and Ni was detected in the effluent, indicating minimal risk of soil pollution. Furthermore, new minerals formed from the dissolution of Ca, Mg, and Fe ions released during basalt weathering, along with other weathering products, transformed soil heavy metals into stable forms, reducing their bioavailability and contributing to the remediation of soil heavy metal pollution.

Abstract:Helium geochemical exploration is a kind of oil and gas geochemical exploration that aims to determine the distribution and resource potential of underground helium by analyzing helium abundance in surface soil samples. While helium has been discovered in theJinzhong basin, dedicated research on helium geochemical exploration in this region remains limited. This study, through the analysis of helium content in soil samples from different geomorphological units and depths, suggests that surface helium abundance is affected by landscape, hydrological conditions, soil properties, and human activities. To minimize human and biological influences, sampling should be carried out at a depth greater than 1. 6 m below the surface, preferably in clay soils with low water saturation and away from areas affected by human activities. Based on the findings, a model for helium geochemical exploration in the Jinzhong basin has been established. Helium, once generated, migrates upwards and escapes together with underground fluids through faults, accumulating in helium- rich gas reservoirs near faults with good sealing properties. In areas with good communication with surface water systems, helium is more likely to escape to the surface, forming surface anomalies. This research provides a foundation for future helium geochemical exploration in this area and can serve as a reference for helium resource investigations in other areas.

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