Journal of Asian Earth Sciences最新文献

{"title":"Fluid source and evolution in Jinchang Au-Ni superimposed deposit, Ailaoshan, southeastern Tibet","authors":"Shiyu Liu ,&nbsp;Huajian Li ,&nbsp;Mengdi Lu ,&nbsp;Ziqing Zhu ,&nbsp;Haoying Chen ,&nbsp;Chaoyi Dong ,&nbsp;Lin Yang ,&nbsp;Wei Ma","doi":"10.1016/j.jseaes.2025.106721","DOIUrl":"10.1016/j.jseaes.2025.106721","url":null,"abstract":"<div><div>The Jinchang deposit in the Ailaoshan Belt, southeastern Tibet, is a unique Au-Ni superimposed deposit, with Miocene gold mineralization over Triassic nickel mineralization. This study aims to detect fluid source and evolution during the two mineralization periods based on geological evidence, He-Ar isotopic analysis of pyrite, and trace elements and sulfur isotopes of sulfides and sulfosalts. Ores occur in wide alteration zones rich in nickel-bearing sulfides during nickel mineralization. The gases released from pyrite have R/Ra radios of 0.002 to 0.03, falling in the field of crustal fluids. The fluids may be derived from an oxidized source or from a reduced source that later evolved to a higher oxidation state before or during mineralization, resulting in strongly negative δ³⁴S values as low as −36.3 ‰. Nickel was leached from the ultramafic rocks during fluid ascent and precipitated by fluid-rock interactions. Ores are characterized by high-angle brecciated quartz veins with minor sulfides during gold mineralization. The gases released from pyrite have R/Ra radios of 0.025 to 0.24, indicating the gold-bearing fluid was derived from the mantle but with little mixing of crustal components. The relatively high mean nickel concentrations in gold-bearing pyrite (2848 ppm) indicate the gold-bearing fluid reacted with the previous nickel ores and/or ultramafic rocks during ascent. The varying δ³⁴S values of tetrahedrite found in gold-bearing veins infiltrating in altered sandstone (−9.1 to −6.5 ‰) and altered slate (−6.1 to −4.0 ‰) indicate that the types and degrees of fluid-rock interactions shifting fluid sulfur isotope compositions during gold mineralization.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"292 ","pages":"Article 106721"},"PeriodicalIF":2.7,"publicationDate":"2025-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144365857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Segmentation of the Manila subduction zone and slab tearing beneath the Philippine mobile belt","authors":"Shu-Kun Hsu ,&nbsp;Wen-Nan Wu ,&nbsp;Lien-Kai Lin ,&nbsp;Shiou-Ya Wang ,&nbsp;Yi-Ching Yeh ,&nbsp;Leo T. Armada ,&nbsp;Carla B. Dimalanta ,&nbsp;Kuan-Ting Chen ,&nbsp;Yun-Jie Tsai ,&nbsp;Ching-Hui Tsai","doi":"10.1016/j.jseaes.2025.106720","DOIUrl":"10.1016/j.jseaes.2025.106720","url":null,"abstract":"<div><div>The Philippine Fault Zone (PFZ) is a key tectonic structure associated with crustal deformation and earthquakes throughout the Philippine Archipelago. Understanding its structures and related mechanisms can significantly mitigate seismic hazards. However, the complete structure of the PFZ, particularly its northwest termination in west Luzon, remains ambiguous. Based on newly acquired multichannel seismic reflection profiles and high-resolution bathymetric data, we have identified four roughly NW-SE trending fault zones off west Luzon, interpreted as branch faults of the northwestward prolongation of the inland PFZ. The southernmost branch could be the offshore extension of the principal NW-SE trending PFZ in central Luzon, terminating at the Manila Trench near ∼ 119°E and ∼ 17.5°N and segmenting the Manila Trench. A new transform fault could be formed to connect the northern and the southern Manila Trench segments. However, the trend of the Manila Trench has changed ∼ 35° counterclockwise from north to south. Coinciding with the NW-SE trending PFZ in central Luzon, the Manila subducting slab beneath central Luzon has been torn, as revealed by seismic tomography and seismicity. The northern subducted slab dips 40° eastward, while the southern slab dips 80° eastward. The segmentation of the Manila subduction zone along the NW-SE trending principal PFZ could be due to the southeastward collision of the Palawan microcontinental block against the Philippine mobile belt near Mindoro and the northwestward docking of the Benham Rise. The segmentation of the Manila subduction zone and slab tearing could dominate regional kinematics and crustal deformation.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"292 ","pages":"Article 106720"},"PeriodicalIF":2.7,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144329925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Revisiting the Indium Window effect: Insights from sphalerite big data","authors":"Qi-Nan Zou ,&nbsp;Yu-Miao Meng ,&nbsp;Rui-Zhong Hu ,&nbsp;Xiao-Wen Huang ,&nbsp;Xian-Wu Bi ,&nbsp;Tai-Ping Zhao","doi":"10.1016/j.jseaes.2025.106719","DOIUrl":"10.1016/j.jseaes.2025.106719","url":null,"abstract":"<div><div>The “Indium Window” effect refers to the preferential enrichment of In in sphalerite within a specific Cd concentration range (0.2–0.6 wt%). This effect was proposed based on an In-rich epithermal deposit. However, the universality of this phenomenon across diverse types of Pb-Zn deposits, as well as the underlying mechanisms governing In enrichment in sphalerite, remain to be systematically investigated. Principal component analysis of sphalerite trace element data was employed to investigate the correlations between In and other elements. The results demonstrate that the “Indium Window” is not universally applicable across all deposit types but is instead confined to specific geological settings. It is prominent in epithermal, skarn, and volcanogenic massive sulfide deposits but is absent in sedimentary exhalative and Mississippi Valley-type deposits. For In-rich Pb-Zn deposits, skarn and epithermal types do exhibit an “Indium Window”. Beyond Cd, an “Fe Peak” was identified, revealing that Fe concentrations significantly influence In enrichment in sphalerite. The distribution of In is also influenced by other elements such as Mn, Cu, Ag, and Sn in sphalerite, particularly those from In-rich deposits. In addition to associated elements, granitic magma-related fluids and high temperature are important factors controlling In enrichment in the Epithermal, Skarn and In-rich deposits.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"292 ","pages":"Article 106719"},"PeriodicalIF":2.7,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144488962","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochronology and geochemistry of the Shengtieling REE-Fe deposit in the Jiao-Liao-Ji belt, North China Craton: Implications for hydrothermal mineralization related to the ∼1.85 Ga tectono-magmatic event","authors":"Xiao-Hui Wang ,&nbsp;Yu-Bo Ma ,&nbsp;Li-Xing Li ,&nbsp;Hou-Min Li ,&nbsp;Yi Wang ,&nbsp;Yang Dai ,&nbsp;Xuan Wu","doi":"10.1016/j.jseaes.2025.106717","DOIUrl":"10.1016/j.jseaes.2025.106717","url":null,"abstract":"<div><div>The rare earth element-iron (REE-Fe) deposits in the Jiao-Liao-Ji belt (JLJB) of the North China Craton (NCC) have significant exploration potential, but their origin remains enigmatic. The Shengtieling REE-Fe deposit is one of the largest occurrences of the sedimentary-metamorphic type, with ores typically consisting of magnetite leptynite enriched in monazite, magnetite, pyrite, and barite. Whole-rock geochemical data of REE-Fe-barren and REE-Fe-rich leptynites suggest a protolith of rhyolite and dacite, which provided the REEs. Zircon grains extracted from magnetite leptynite are characterized by core-rim textures. <em>In situ</em> U-Pb dating of zircon cores and rims yielded weighted mean ²⁰⁷Pb/²⁰⁶Pb ages of 2161 ± 12 Ma and 1837 ± 9 Ma. The obtained ages indicate the timing of the magmatic protolith formation and the subsequent metamorphism. Additionally, ore mineral monazite grains separated from magnetite leptynite yielded a weighted mean ²⁰⁷Pb/²⁰⁶Pb age of 1843 ± 7 Ma, interpreted as the most reliable estimate for the timing of REE-Fe mineralization. This mineralization was likely linked to the ca. 1.85 Ga metamorphic-hydrothermal event. <em>In situ</em> trace element data of pyrite intergrown with magnetite and monazite indicate that mineralization-related hydrothermal fluids contributed part of the REEs, leached additional REEs from the protolith, and mobilized iron and phosphorus from the Li’eryu Formation under 307–521 °C, acidic, reducing, and low oxygen fugacity (<em>f</em>O₂). Considering that the Co-rich pyrite in the Shengtieling deposit is synchronous with many other occurrences documented in the JLJB, we propose that the ∼1.85 Ga tectono-magmatic event likely had a significant impact on polymetallic mineralization.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"292 ","pages":"Article 106717"},"PeriodicalIF":2.7,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144480327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mineral prospectivity prediction from airborne magnetic data based on the RPCA-ResNet hybrid learning framework","authors":"Zhenyu Fan ,&nbsp;Shengqing Xiong ,&nbsp;Tengfei Ge ,&nbsp;Jingzi He ,&nbsp;Xue Yang ,&nbsp;Yao Liu ,&nbsp;Jianfu Luo","doi":"10.1016/j.jseaes.2025.106718","DOIUrl":"10.1016/j.jseaes.2025.106718","url":null,"abstract":"<div><div>The growing demand for mineral resources in China, coupled with the depletion of shallow iron ore deposits, necessitates advanced exploration technologies for deep-seated concealed mineralization. This study presents an integrated deep learning framework, termed RPCA-ResNet, which combines Robust Principal Component Analysis (RPCA) with deep residual networks to address critical challenges in aeromagnetic interpretation and iron ore prediction within the Central Shandong metallogenic belt, China. Aeromagnetic data were processed using the Inexact Augmented Lagrange Multiplier (IALM) algorithm to implement RPCA, enabling effective separation of weak magnetic anomalies from complex geological backgrounds and demonstrating spatial alignment with borehole-confirmed targets. The proposed RPCA-ResNet architecture integrates multi-scale magnetic features and residual learning mechanisms, resolving gradient vanishing issues in conventional CNNs. Validation results reveal 85.17 % prediction accuracy, 7 ∼ 12 % higher than support vector and decision tree regressions. Finally predict the mineral potential map of iron ore resources in the entire region. The framework reduces exploration areas, demonstrating practical value in the Quaternary coverage area. This methodology establishes a new paradigm for intelligent mineral exploration, effectively bridging geophysical Aeromagnetic signal processing with the advantages of deep learning.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"292 ","pages":"Article 106718"},"PeriodicalIF":2.7,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144480328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Longhua, the first five-element (Ni-Co-As-Ag-Bi) hydrothermal vein deposit in China: Constraints from mineral characteristics and fluid evolution","authors":"Xinshuo Huang ,&nbsp;Mingjian Cao ,&nbsp;Baolin Zhang ,&nbsp;Noreen J. Evans ,&nbsp;Zengsheng Li ,&nbsp;Xinyu Zou ,&nbsp;Shuo Wang ,&nbsp;Pengfei Shan ,&nbsp;Junyu Li ,&nbsp;Guangming Li ,&nbsp;Kezhang Qin","doi":"10.1016/j.jseaes.2025.106712","DOIUrl":"10.1016/j.jseaes.2025.106712","url":null,"abstract":"<div><div>The Longhua deposit is a vein-type Ni-Co deposit in South China, known for its ultrahigh grades of Ni (6.48 %) and Co (0.44 %), which has attracted considerable attention. However, the classification of the deposit remains disputed, presenting challenges for comprehensive metallogenic studies. This study primarily investigates the mineral characteristics and fluid evolution of the deposit, which is characterized by the following features: (1) It hosts a Ni-Co-As-Ag-Bi assemblage within steeply dipping quartz-calcite veins; (2) It contains Ni-Co-Fe arsenides, sulfarsenides, sulfides and native Bi with special fern-like and spherical textures; (3) The ore minerals precipitate from the stage of arsenide (monoarsenide → diarsenide → triarsenide), to sulfarsenide, and ultimately to sulfide, aligning with the elemental sequence of Ni → Co → Fe in each stage and overall transition from As to S; (4) The ore-forming fluids are characterized by medium-to-low temperatures (230 − 90 °C) and are enriched in CH₄. Together, these findings indicate that the deposit could be classified as a five-element (Ni-Co-As-Ag-Bi) hydrothermal vein deposit. The reduction of the ore-forming fluid, attributed to the oxygen fugacity buffering effect of CH₄-organic carbon derived from the thermal decomposition of the host black shales, probably plays a significant role in generating the mineral sequence. The final sulfide stage formed at a higher oxygen fugacity, likely due to the consumption of the black shales, which reduced the overall reducing capacity. The Longhua deposit is the first five-element hydrothermal vein deposit in China, and provides an excellent example for investigating the complete formation processes.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"292 ","pages":"Article 106712"},"PeriodicalIF":2.7,"publicationDate":"2025-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144321007","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unprecedented tantalum enrichment of zircon through stepwise crystallization in Li-Pegmatite, Uljin, South Korea","authors":"Changyun Park ,&nbsp;Jaehwan Kim ,&nbsp;Youseong Lee","doi":"10.1016/j.jseaes.2025.106709","DOIUrl":"10.1016/j.jseaes.2025.106709","url":null,"abstract":"<div><div>This study investigates the unprecedented enrichment of tantalum (Ta) and the stepwise crystallization of zircon in the Li-pegmatite from the Boam mine area, Uljin, South Korea. In the studied pegmatite, three types of zircon—high-uranium (U) zircon, high-tantalum (Ta) zircon, and high-hafnium (Hf) zircon were identified in correspondence with the melt evolution stage. Remarkably, the Ta-rich zircon exhibited an exceptionally high Ta concentration of up to 6.31 wt%, the highest ever reported. The findings suggest that the Ta-rich zircon is crystallized under the influence of an extremely fractionated, Li-, F-enriched and P-poor melt. Considering that the studied pegmatite originates from a Ta-depleted melt, this phenomenon indicates that Ta enrichment in zircon depends more on the melt composition rather than the Ta content in the melt. Furthermore, since the aqueous fluid expelled from the melt facilitates the recrystallization of structurally unstable zircon, fluid influence should be minimized for the preservation of Ta-rich zircon. These findings offer critical insights for behavior of tantalum and zirconium during formation of rare-metal pegmatites.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"292 ","pages":"Article 106709"},"PeriodicalIF":2.7,"publicationDate":"2025-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144312933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The role of windfield, sedimentary sources, and basin structure in the formation of beach-bar deposition systems: A case study in Paleogene Shahejie formation in the Zhanhua Sag of the Bohai Bay Basin, China","authors":"Changyin Shao,&nbsp;Fan Song,&nbsp;Longwei Qiu,&nbsp;Shiqi Zhang,&nbsp;Qingyuan Kong","doi":"10.1016/j.jseaes.2025.106713","DOIUrl":"10.1016/j.jseaes.2025.106713","url":null,"abstract":"<div><div>Beach bar systems, as significant reservoirs in terrestrial lacustrine basins, have led to notable progress in understanding their formation mechanisms and controlling factors. However, under the complex basin setting during the fault-depression transition period, the distribution patterns, controlling mechanisms, and hydrocarbon exploration potential of different beach bar types remain poorly constrained. This study focuses on the Paleogene Second Member (Es2) in the Zhanhua Sag, Bohai Bay Basin, China, integrating well logs, core data, and 3D seismic interpretation to systematically analyze the sedimentary characteristics, dominant controls, and exploration potential of beach bar deposits. Three types are identified in the Es2: sandstone beach bars, carbonate-dominated beach bars, and clastic-dominated beach bars. Vertically, the scale of these deposits gradually increases from Part 4 to Part 1, while laterally, their distribution follows a tripartite coupling mechanism involving windfield, sedimentary sources, and basin structure: northeast-trending windfields drive wave action to form northwest-southeast-oriented beach bars; sediment supply intensity determines beach bar lithology (sandstone-dominated in high-supply zones vs. carbonate-dominated in low-supply zones); and the unique basin structure (steep slope–deep water–gentle slope) during the fault-depression transition controlled spatial differentiation. Reservoir characterization shows high porosity (25 %–30 %) but low permeability (20–50 mD), with 2–6 m thick sandy bars serving as prime exploration targets. In particular, stacked beach bars interbedded with mudstone seals in the southern gentle slope exhibit superior hydrocarbon accumulation conditions. These findings elucidate the genetic mechanisms of beach bars during a tectonic transition and their hydrocarbon enrichment patterns, providing critical geological references for lithologic reservoir exploration in analogous basins.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"291 ","pages":"Article 106713"},"PeriodicalIF":2.7,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144279420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-speed anomaly zone beneath the Changbaishan volcanic province in NE China: Insights from simulation of the Cenozoic Pacific plate subduction using geodynamic models with data assimilation","authors":"Tao Zhu ,&nbsp;Diandian Peng ,&nbsp;Lijun Liu","doi":"10.1016/j.jseaes.2025.106714","DOIUrl":"10.1016/j.jseaes.2025.106714","url":null,"abstract":"<div><div>Seismic tomographic studies have revealed a high-speed anomaly zone with a length exceeding 1300 km within the mantle transition zone (MTZ) beneath the Changbaishan volcanic province (CVP) in Northeast China. This anomaly zone has often been attributed to the Pacific slab. However, the velocity structure of its western part differs significantly from that of its eastern part, with a boundary at approximately 120°E. To explore its origin, we have developed a series of three-dimensional (3D) regional thermochemical geodynamic models incorporating data assimilation, based on a global model. These models aim to reproduce the dynamic subduction process of the Pacific slab since the Cenozoic for tracking the structure of the high-speed anomaly zone. According to our preferred model, prior to 25 Ma, the Pacific plate was characterized by flat subduction driven by a strong horizontal flow resulting from the sinking of the Izanagi slab, which had subducted into the MTZ during the Mesozoic. Between 25 Ma and 20 Ma, the Pacific plate underwent significant downward subduction, followed by rapid westward movement over a long distance of ∼1200 km within the MTZ after 20 Ma. Some isolated subducted slabs, which originated from the flat subduction that took place prior to 25 Ma, were attached to the top of the main subducted Pacific slab ∼15 Ma ago. These slabs eventually merged with the main slab by ∼10 Ma. This merging of the main subducted Pacific slab and the isolated subducted slabs primarily accounts for the high-speed anomaly zone in the eastern region. Meanwhile, another isolated subducted slab began to come into contact with the westernmost end of the main subducted Pacific slab at ∼5 Ma and has remained tightly coupled up to the present day, suggesting that the western part of the anomaly zone is likely caused solely by the isolated subducted slab. Furthermore, our study presents an alternative, computationally resource-saving and feasible approach for modeling stagnant slabs in East Asia. This approach utilizes a regional model, with the viscosity and temperature fields derived from a global model serving as initial conditions, thereby complementing existing global models.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"291 ","pages":"Article 106714"},"PeriodicalIF":2.7,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144291008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Controls of provenance changes and chemical weathering on organic matter accumulation in lacustrine basins: A case study of the early–middle Eocene Wenchang Formation in the eastern Yangjiang Sag, Pearl River Mouth Basin, northern South China Sea","authors":"Chuan Xu ,&nbsp;Guangrong Peng ,&nbsp;Pei Liu ,&nbsp;Xuanlong Shan ,&nbsp;Guoli Hao ,&nbsp;Peimeng Jia ,&nbsp;Kang Li","doi":"10.1016/j.jseaes.2025.106711","DOIUrl":"10.1016/j.jseaes.2025.106711","url":null,"abstract":"<div><div>Lacustrine sedimentary environments occurred widespread along the northern continental margin of the South China Sea (SCS) during the early–middle Eocene, and the large-scale organic-rich lacustrine mudstone of the Wenchang Formation in the Pearl River Mouth Basin (PRMB) was deposited during this period. These lacustrine source rocks provide excellent research opportunities for revealing provenance evolution during the early–middle Eocene in the northern SCS and its influence on the formation of organic-rich mudstone. In this study, the influences of provenance evolution and weathering on the formation of organic-rich mudstone during the early–middle Eocene were examined via new elemental geochemical data from the Wenchang Formation mudstone in the PRMB combined with compiled zircon geochronology data from basement magmatic rocks and Paleogene sandstone. Notably, Co/Th–La/Sc, La/Th–Hf, and Th–Sc–Zr/10 discrimination diagrams suggested a felsic volcanic provenance for the Wenchang Formation, and detrital zircon geochronology revealed two dominant age peaks from 110 to 116 Ma and 151–159 Ma. Integrated with tectonic geomorphic analysis, late Jurassic to early Cretaceous magmatic rocks in peripheral low-uplift zones of the secondary basin served as primary contributors to the sedimentary provenance of the Wenchang Formation. The low Ti/K ratios suggested low terrigenous clastic input during the deposition of the Wenchang Formation, which was associated with small- and medium-sized sediments supplied from low-uplift areas along the periphery of secondary basins. Furthermore, the positive correlations between the Ti/K ratio and the total organic carbon (TOC) and P₂O₅ contents indicated that the relatively low terrigenous input not only increased the utilization efficiency of lacustrine nutrients (e.g., P and K) but also minimized dilution effects, thereby facilitating organic matter (OM) burial in lacustrine mudstones in the eastern Yangjiang Sag (EYJS). Additionally, the combination of elevated U/Th ratios, high chemical index of alteration (CIA) values and high plagioclase index of alteration (PIA) values collectively constrained moderate to intense chemical weathering during the early–middle Eocene. The coupled relationships between the chemical weathering intensity, lacustrine productivity, and TOC accumulation suggested that enhanced terrestrial weathering likely accelerated hydrological cycling, increased lacustrine productivity, and promoted OM enrichment in these mudstones. Consequently, the interplay between pronounced chemical weathering and moderate terrigenous input during the early–middle Eocene exerted critical control on the development of high-quality lacustrine source rocks in the EYJS of the PRMB. These findings provide significant insights for hydrocarbon exploration in the northern SCS marginal basin group.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"291 ","pages":"Article 106711"},"PeriodicalIF":2.7,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144297201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}