Pub Date : 2025-12-23DOI: 10.1016/j.jseaes.2025.106939
Anliang Liu , Lifang Wang , Zhihong Chen , Xinquan Liang , Hong Lu
Evaporative fractionation has been recognized as a pivotal mechanism shaping hydrocarbon accumulation, yet the precise geochemical fingerprints and underlying controls of this process remain incompletely resolved. Here, we present an integrated geochemical investigation of crude oils from both basins, utilizing whole-oil chromatograms, light hydrocarbon and n-alkane distributions, diamondoid compositions, and stable carbon isotopic signatures, in conjunction with regional tectonic and geological analyses. Our findings reveal that crude oils throughout both basins have experienced diverse degrees of evaporative fractionation, as evidenced by the preferential depletion of low-carbon-number n-alkanes and adamantanes in concert with migrating natural gas, together with enrichment of aromatic hydrocarbons and diamantanes. These alterations generate a negative correlation between the ratio of adamantane-to-diamantane (As/Ds) and n-alkanes mass depletion, while the loss of light compositions gives rise to heavier δ13C values of whole-oil. This manifests clearly as an inverted “V-shaped” isotopic profile among the saturates, whole oil, and aromatic hydrocarbon fractions, which offers a robust geochemical indicator of evaporative fractionation. Petroleum system analysis indicates that this process is primarily governed by three factors: (1) abundant source rocks, which provide the requisite supply of light hydrocarbons; (2) distinct hydrocarbon migration networks, including vertical diapiric conduits and faults; and (3) the effects of late-stage charging by highly-mature natural gas, often in association with episodic reservoir leakage.
{"title":"Geochemical responses and principal controlling factors of evaporative fractionation in crude oils from the Yinggehai and Qiongdongnan basins, South China Sea, China","authors":"Anliang Liu , Lifang Wang , Zhihong Chen , Xinquan Liang , Hong Lu","doi":"10.1016/j.jseaes.2025.106939","DOIUrl":"10.1016/j.jseaes.2025.106939","url":null,"abstract":"<div><div>Evaporative fractionation has been recognized as a pivotal mechanism shaping hydrocarbon accumulation, yet the precise geochemical fingerprints and underlying controls of this process remain incompletely resolved. Here, we present an integrated geochemical investigation of crude oils from both basins, utilizing whole-oil chromatograms, light hydrocarbon and <em>n</em>-alkane distributions, diamondoid compositions, and stable carbon isotopic signatures, in conjunction with regional tectonic and geological analyses. Our findings reveal that crude oils throughout both basins have experienced diverse degrees of evaporative fractionation, as evidenced by the preferential depletion of low-carbon-number <em>n</em>-alkanes and adamantanes in concert with migrating natural gas, together with enrichment of aromatic hydrocarbons and diamantanes. These alterations generate a negative correlation between the ratio of adamantane-to-diamantane (As/Ds) and <em>n</em>-alkanes mass depletion, while the loss of light compositions gives rise to heavier δ<sup>13</sup>C values of whole-oil. This manifests clearly as an inverted “V-shaped” isotopic profile among the saturates, whole oil, and aromatic hydrocarbon fractions, which offers a robust geochemical indicator of evaporative fractionation. Petroleum system analysis indicates that this process is primarily governed by three factors: (1) abundant source rocks, which provide the requisite supply of light hydrocarbons; (2) distinct hydrocarbon migration networks, including vertical diapiric conduits and faults; and (3) the effects of late-stage charging by highly-mature natural gas, often in association with episodic reservoir leakage.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"298 ","pages":"Article 106939"},"PeriodicalIF":2.4,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978236","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}
Pub Date : 2025-12-23DOI: 10.1016/j.jseaes.2025.106904
Huaibo Zhao , Shuping Chen , Timothy Chris Schmid , Haowei Yuan , Weijia Zhan , Fan Wang
Salt-bearing fold-and-thrust belts (FTBs) in foreland basins exhibit complex structural architectures, primarily governed by the interplay among basement geometry, supra-salt mechanical strength, and the detachment behavior of intervening salt layers. However, the respective roles of basement surface geometry and supra-salt cohesion in controlling deformation localization, thrust segmentation, and fold development remain poorly constrained, particularly in regions with limited subsalt seismic imaging. To address this gap, we conducted two-dimensional discrete element method (DEM) simulations to systematically assess how variations in basement surface geometry and supra-salt cohesion influence the structural evolution of salt-bearing FTBs. The results show that lateral variations in basement morphology produce significant heterogeneity in salt layer thickness, thereby strongly influencing salt particle rearrangement and deformation localization. Redistribution of salt particles from thick to thin zones leads to compression and uplift in the overburden, while reverse movement induces extension and subsidence. A relatively low supra-salt cohesion promotes more rapid deformation front propagation, increased fold density, and more frequent salt piercement, whereas a relatively high cohesion delays deformation front propagation and favors fewer but higher-amplitude folds and enhanced thrust faulting. Comparisons with representative natural examples demonstrate that the models broadly capture the main structural features of salt-related FTBs at a regional scale, including large-scale thrust systems and salt-cored folds. Overall, our findings highlight that basement relief and supra-salt cohesion are first-order controls on structural evolution in compressional salt-bearing systems, thereby enhancing the understanding of deformation localization, thrust segmentation, and fold development.
{"title":"Constraints of basement geometry and supra-salt cohesion on deformation of salt-bearing fold-and-thrust belts: a discrete-element study","authors":"Huaibo Zhao , Shuping Chen , Timothy Chris Schmid , Haowei Yuan , Weijia Zhan , Fan Wang","doi":"10.1016/j.jseaes.2025.106904","DOIUrl":"10.1016/j.jseaes.2025.106904","url":null,"abstract":"<div><div>Salt-bearing fold-and-thrust belts (FTBs) in foreland basins exhibit complex structural architectures, primarily governed by the interplay among basement geometry, supra-salt mechanical strength, and the detachment behavior of intervening salt layers. However, the respective roles of basement surface geometry and supra-salt cohesion in controlling deformation localization, thrust segmentation, and fold development remain poorly constrained, particularly in regions with limited subsalt seismic imaging. To address this gap, we conducted two-dimensional discrete element method (DEM) simulations to systematically assess how variations in basement surface geometry and supra-salt cohesion influence the structural evolution of salt-bearing FTBs. The results show that lateral variations in basement morphology produce significant heterogeneity in salt layer thickness, thereby strongly influencing salt particle rearrangement and deformation localization. Redistribution of salt particles from thick to thin zones leads to compression and uplift in the overburden, while reverse movement induces extension and subsidence. A relatively low supra-salt cohesion promotes more rapid deformation front propagation, increased fold density, and more frequent salt piercement, whereas a relatively high cohesion delays deformation front propagation and favors fewer but higher-amplitude folds and enhanced thrust faulting. Comparisons with representative natural examples demonstrate that the models broadly capture the main structural features of salt-related FTBs at a regional scale, including large-scale thrust systems and salt-cored folds. Overall, our findings highlight that basement relief and supra-salt cohesion are first-order controls on structural evolution in compressional salt-bearing systems, thereby enhancing the understanding of deformation localization, thrust segmentation, and fold development.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"298 ","pages":"Article 106904"},"PeriodicalIF":2.4,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145885707","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}
Pub Date : 2025-12-23DOI: 10.1016/j.jseaes.2025.106937
Beiyu Zhou , Bin Huang , Manoj K. Pandit , Wei Wang
Geochronological and geochemical data from mafic intrusions in the Aravalli Craton provide critical insights into the paleogeographic reconstruction of NW India within the Kenorland and Columbia supercontinents. The late Archean Udaipur mafic dykes (2572 ± 12 Ma) display elevated Zr/Nb (12.0–19.2), La/Nb (1.67–3.11) and Ba/Nb (9.62–225) and low Ti/Zr (97.3–100) ratios, indicating derivation from a spinel lherzolite mantle source metasomatized by subduction-related fluids. On the other hand, the Paleoproterozoic Khetri mafic dykes (1848 ± 9 Ma) show comparable Zr/Nb, La/Nb, and Ba/Nb but distinctly higher Th/Nb (1.23–1.32) and Th/Zr (0.11–0.13) ratios, suggesting their derivation from a garnet-spinel lherzolite mantle source metasomatized by both arc-related fluids and melts derived from subducted sediments. The subduction-related geochemical signatures of the ca. 2.57 Ga Udaipur mafic intrusions indicate prolonged arc-related magmatic process characterized by mantle underplating played a vital role in the stabilization of the Aravalli Craton during the late Archean. In contrast, the transitional geochemical characteristics of the ca. 1.85 Ga Khetri mafic rocks mark a tectonic transition from subduction-related to extensional regimes during the Columbia supercontinent assembly. Temporal and geochemical correlations between these mafic magmatic events and coeval ones in the South Indian, Western Australian, and North China cratons support the models suggesting a close spatial proximity of these cratonic blocks during both the late Archean Kenorland (ca. 2.7–2.5 Ga) and the Paleoproterozoic Columbia supercontinent amalgamation processes (ca. 2.0–1.8 Ga).
{"title":"Late Archean–early Proterozoic mafic intrusions in the Aravalli Craton (NW India): Implications for the reconstruction of the Kenorland and Columbia supercontinents","authors":"Beiyu Zhou , Bin Huang , Manoj K. Pandit , Wei Wang","doi":"10.1016/j.jseaes.2025.106937","DOIUrl":"10.1016/j.jseaes.2025.106937","url":null,"abstract":"<div><div>Geochronological and geochemical data from mafic intrusions in the Aravalli Craton provide critical insights into the paleogeographic reconstruction of NW India within the Kenorland and Columbia supercontinents. The late Archean Udaipur mafic dykes (2572 ± 12 Ma) display elevated Zr/Nb (12.0–19.2), La/Nb (1.67–3.11) and Ba/Nb (9.62–225) and low Ti/Zr (97.3–100) ratios, indicating derivation from a spinel lherzolite mantle source metasomatized by subduction-related fluids. On the other hand, the Paleoproterozoic Khetri mafic dykes (1848 ± 9 Ma) show comparable Zr/Nb, La/Nb, and Ba/Nb but distinctly higher Th/Nb (1.23–1.32) and Th/Zr (0.11–0.13) ratios, suggesting their derivation from a garnet-spinel lherzolite mantle source metasomatized by both arc-related fluids and melts derived from subducted sediments. The subduction-related geochemical signatures of the ca. 2.57 Ga Udaipur mafic intrusions indicate prolonged arc-related magmatic process characterized by mantle underplating played a vital role in the stabilization of the Aravalli Craton during the late Archean. In contrast, the transitional geochemical characteristics of the ca. 1.85 Ga Khetri mafic rocks mark a tectonic transition from subduction-related to extensional regimes during the Columbia supercontinent assembly. Temporal and geochemical correlations between these mafic magmatic events and coeval ones in the South Indian, Western Australian, and North China cratons support the models suggesting a close spatial proximity of these cratonic blocks during both the late Archean Kenorland (ca. 2.7–2.5 Ga) and the Paleoproterozoic Columbia supercontinent amalgamation processes (ca. 2.0–1.8 Ga).</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"298 ","pages":"Article 106937"},"PeriodicalIF":2.4,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145885704","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}
Pub Date : 2025-12-22DOI: 10.1016/j.jseaes.2025.106933
Jianling Cao , Yaolin Shi , Hui Wang , Xiaoxia Liu
The middle segment of the Red River fault (RRF) in southwestern China has historically lacked large earthquakes, unlike its parallel northern fault zone. To explain the reason for the absence of historical seismicity on the middle RRF, we developed a 3D viscoelastic–plastic model simulating slip partitioning between these structures, using GNSS and short-baseline geodetic constraints. The simulated horizontal velocities match observations well. Based on data fitting, the optimal mechanical parameters are determined as follows: a fault viscosity of 1019 Pa·s, and plastic yield strengths of 10 MPa and 20 MPa for the straight and Big Bend sections of the middle segment of the RRF, respectively; the corresponding dextral slip rates are: 1.5 mm/a for the straight RRF section, 1.0–1.5 mm/a for its Big Bend section, 1.0–1.5 mm/a for the Chuxiong fault, 2.5–3.0 mm/a for the Qujiang fault, and 0.5 mm/a for the Shiping fault. Slip rates are more sensitive to plastic yield strength than viscosity, as simulations exceed viscoelastic relaxation time. Estimated recurrence intervals with slip rates we obtain for M 7–8 earthquakes on the middle segment of the RRF range from 1200 to 3500 years. This long recurrence interval—compared to local earthquake written history about four to five centuries in the region—may explain the absence of large historical earthquakes on the middle segment of the RRF. Another possible reason is that the middle RRF may currently be in a seismically quiescent period if its parallel strike-slip faults alternate in activity.
{"title":"Middle segment of the Red River fault: Numerical simulation of slip rates with implications for the absence of major historical earthquakes","authors":"Jianling Cao , Yaolin Shi , Hui Wang , Xiaoxia Liu","doi":"10.1016/j.jseaes.2025.106933","DOIUrl":"10.1016/j.jseaes.2025.106933","url":null,"abstract":"<div><div>The middle segment of the Red River fault (RRF) in southwestern China has historically lacked large earthquakes, unlike its parallel northern fault zone. To explain the reason for the absence of historical seismicity on the middle RRF, we developed a 3D viscoelastic–plastic model simulating slip partitioning between these structures, using GNSS and short-baseline geodetic constraints. The simulated horizontal velocities match observations well. Based on data fitting, the optimal mechanical parameters are determined as follows: a fault viscosity of 10<sup>19</sup> Pa·s, and plastic yield strengths of 10 MPa and 20 MPa for the straight and Big Bend sections of the middle segment of the RRF, respectively; the corresponding dextral slip rates are: 1.5 mm/a for the straight RRF section, 1.0–1.5 mm/a for its Big Bend section, 1.0–1.5 mm/a for the Chuxiong fault, 2.5–3.0 mm/a for the Qujiang fault, and 0.5 mm/a for the Shiping fault. Slip rates are more sensitive to plastic yield strength than viscosity, as simulations exceed viscoelastic relaxation time. Estimated recurrence intervals with slip rates we obtain for <em>M</em> 7–8 earthquakes on the middle segment of the RRF range from 1200 to 3500 years. This long recurrence interval—compared to local earthquake written history about four to five centuries in the region—may explain the absence of large historical earthquakes on the middle segment of the RRF. Another possible reason is that the middle RRF may currently be in a seismically quiescent period if its parallel strike-slip faults alternate in activity.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"298 ","pages":"Article 106933"},"PeriodicalIF":2.4,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145842657","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}
Pub Date : 2025-12-22DOI: 10.1016/j.jseaes.2025.106918
Falak Sheir , Jiafu Chen , Yichang Liu , Xu Ma , Wei Li , Yuqi Liu , Yi Zhang , Zhenghe Zhao
The collision between the Bainaimiao arc belt and the North China Craton, and the subsequent closure of the Paleo-Asian Ocean, are two major tectonic events for the Central Asian Orogenic Belt. However, the timing of these events remains controversial because the deformation fabrics that record crucial information about the collision history are poorly constrained. To address this, we conducted detailed structural analysis, quartz c-axis fabric analysis, and zircon U-Pb geochronology of the ductile deformation fabrics within the Chenjiatun shear zone, located east of the Bainaimiao arc belt. The structural analysis indicates that the deformation zone records two main ductile deformation events, D1 and D2, defined by S1 and S2 foliations. The S1 foliations (D1) trend ESE, plunge SE, and the S2 foliations (D2) trend ENE & NE, plunge NW & SE, respectively. Each deformation event is further subdivided into early-late sub-stages based on differences in fabric orientation and deformation characteristics. The D1a and D2 display dextral strike-slip shearing, while D1b involves sinistral strike-slip shearing. Microstructures and quartz c-axis patterns indicate that D1 occurred at high-temperature conditions (∼600–700 °C) under amphibolite facies conditions and D2 at medium temperature (∼400–500 °C) under upper green-schist facies conditions. The zircon U–Pb dating reveals that the deformation occurred at 423 Ma for D1b, 264–261 Ma for D2a, and 260–243 Ma for D2b. These results, combined with previous data, conclude that the D1 event records the Late Silurian Bainaimiao arc belt-North China Craton collision, while the D2 event represents the initial- to -final closure of the Paleo-Asian Ocean, which occurred from the Middle Permian to the Middle Triassic, followed by an intra-continental collision to the east of the Bainaimiao arc belt within the southeastern Central Asian Orogenic Belt.
{"title":"Late Silurian arc-continent collision and Permian-Triassic closure of Paleo-Asian Ocean in southeastern Central Asian Orogenic Belt: insight from the multiphase deformation from the eastern Bainaimiao arc belt, China","authors":"Falak Sheir , Jiafu Chen , Yichang Liu , Xu Ma , Wei Li , Yuqi Liu , Yi Zhang , Zhenghe Zhao","doi":"10.1016/j.jseaes.2025.106918","DOIUrl":"10.1016/j.jseaes.2025.106918","url":null,"abstract":"<div><div>The collision between the Bainaimiao arc belt and the North China Craton, and the subsequent closure of the Paleo-Asian Ocean, are two major tectonic events for the Central Asian Orogenic Belt. However, the timing of these events remains controversial because the deformation fabrics that record crucial information about the collision history are poorly constrained. To address this, we conducted detailed structural analysis, quartz c-axis fabric analysis, and zircon U-Pb geochronology of the ductile deformation fabrics within the Chenjiatun shear zone, located east of the Bainaimiao arc belt. The structural analysis indicates that the deformation zone records two main ductile deformation events, D1 and D2, defined by S1 and S2 foliations. The S1 foliations (D1) trend ESE, plunge SE, and the S2 foliations (D2) trend ENE & NE, plunge NW & SE, respectively. Each deformation event is further subdivided into early-late sub-stages based on differences in fabric orientation and deformation characteristics. The D1a and D2 display dextral strike-slip shearing, while D1b involves sinistral strike-slip shearing. Microstructures and quartz c-axis patterns indicate that D1 occurred at high-temperature conditions (∼600–700 °C) under amphibolite facies conditions and D2 at medium temperature (∼400–500 °C) under upper green-schist facies conditions. The zircon U–Pb dating reveals that the deformation occurred at 423 <!--> <!-->Ma for D1b, 264–261 Ma for D2a, and 260–243 Ma for D2b. These results, combined with previous data, conclude that the D1 event records the Late Silurian Bainaimiao arc belt-North China Craton collision, while the D2 event represents the initial- to -final closure of the Paleo-Asian Ocean, which occurred from the Middle Permian to the Middle Triassic, followed by an intra-continental collision to the east of the Bainaimiao arc belt within the southeastern Central Asian Orogenic Belt.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"298 ","pages":"Article 106918"},"PeriodicalIF":2.4,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145842659","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}
Pub Date : 2025-12-22DOI: 10.1016/j.jseaes.2025.106935
Khizar Hayat , Laixi Tong , Zhao Liu , Christopher J.L. Wilson , Xiaohan Liu , Kexin Wu , Xinyue Han
The metamorphic evolution of the Higher Himalayan rocks in southern Tibet has been characterized through detailed studies of metapelites, whereas the associated amphibolites remain largely unexplored. In this paper, we describe detailed petrography, mineral chemistry, phase-equilibrium modeling, and zircon U-Pb ages of garnet-bearing amphibolites in the Cona area, southern Tibet. The rocks record three distinct metamorphic stages M1, M2, and M3. Prograde stage (M1) is defined by a mineral assemblage of garnet with amphibole, biotite, and plagioclase, crystallized under pressure–temperature (P-T) conditions of 9.5 kbar and 720 °C. Peak metamorphic stage (M2) is characterized by the existence of garnet, amphibole, biotite, plagioclase, quartz, ilmenite, and rutile, with P-T conditions of 12 kbar and 810 °C. Retrograde stage (M3) comprising garnet, K-feldspar, plagioclase, and quartz, stable at 8.5 kbar and 710 °C. U-Pb ages of zircon indicate that these amphibolites experienced anatectic metamorphism between 28 and 15 Ma. There is an increase in the metamorphic thermobaric ratios from 675–835 °C/GPa to 875 °C/GPa, rising the geothermal gradients from 18.2 °C/km to 24.8 °C/km. Integrating our results with previous studies, it is concluded that the Cona amphibolites underwent peak HP metamorphism, followed by a decompressional path similar to that of Cona metapelites during the Miocene, reflecting a phase of post-collisional rapid exhumation.
{"title":"Miocene high-pressure metamorphism of garnet-bearing amphibolites in the Cona area, southern Tibet: Insights into the tectonic evolution of the Higher Himalaya","authors":"Khizar Hayat , Laixi Tong , Zhao Liu , Christopher J.L. Wilson , Xiaohan Liu , Kexin Wu , Xinyue Han","doi":"10.1016/j.jseaes.2025.106935","DOIUrl":"10.1016/j.jseaes.2025.106935","url":null,"abstract":"<div><div>The metamorphic evolution of the Higher Himalayan rocks in southern Tibet has been characterized through detailed studies of metapelites, whereas the associated amphibolites remain largely unexplored. In this paper, we describe detailed petrography, mineral chemistry, phase-equilibrium modeling, and zircon U-Pb ages of garnet-bearing amphibolites in the Cona area, southern Tibet. The rocks record three distinct metamorphic stages M1, M2, and M3. Prograde stage (M1) is defined by a mineral assemblage of garnet with amphibole, biotite, and plagioclase, crystallized under pressure–temperature (P-T) conditions of 9.5 kbar and 720 °C. Peak metamorphic stage (M2) is characterized by the existence of garnet, amphibole, biotite, plagioclase, quartz, ilmenite, and rutile, with P-T conditions of 12 kbar and 810 °C. Retrograde stage (M3) comprising garnet, K-feldspar, plagioclase, and quartz, stable at 8.5 kbar and 710 °C. U-Pb ages of zircon indicate that these amphibolites experienced anatectic metamorphism between 28 and 15 Ma. There is an increase in the metamorphic thermobaric ratios from 675–835 °C/GPa to 875 °C/GPa, rising the geothermal gradients from 18.2 °C/km to 24.8 °C/km. Integrating our results with previous studies, it is concluded that the Cona amphibolites underwent peak HP metamorphism, followed by a decompressional path similar to that of Cona metapelites during the Miocene, reflecting a phase of post-collisional rapid exhumation.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"298 ","pages":"Article 106935"},"PeriodicalIF":2.4,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145842656","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}
Pub Date : 2025-12-22DOI: 10.1016/j.jseaes.2025.106936
Shuangqi Feng , Hancheng Ji , Liang Chen , Xuegui Jiang , Pengfei Xiang , Yanqing Shi , Chunfu Liao , Ying Liu , Ling Li
In recent years, the penetration of meteoric water through unconformities and porous sandstones, and its subsequent dissolution effects within deep-seated reservoirs, has attracted widespread attention. Assessing whether a diagenetic system is open or closed is crucial for evaluating how dissolution influences reservoir quality. However, for structural uplifts with large-scale, deep-seated faults, how dissolution from meteoric water leaching varies spatially from the structural high to the downdip slope, and the resulting reservoir characteristics, remain poorly understood. To address this, we conducted an integrated analysis of diagenetic mineral assemblages and the associated paragenetic sequence in the Middle Jurassic reservoir of the Hongciliang tectonic belt, Yabulai Basin. Methods included thin-section petrography, scanning electron microscopy (SEM), isotopic testing, X-ray diffraction (XRD), reservoir porosity–permeability measurements, and computerized tomography (CT) scanning. Results demonstrate that the medium- to fine-grained arkoses in the Hongciliang tectonic belt were deposited under similar sedimentary environments. Nevertheless, differential dissolution, coupled with mass transfer and re-precipitation of dissolved materials, results in substantial differences between the structural high and downdip slope. These differences are manifested in the development of dissolution pores, as well as in the types and abundances of authigenic minerals within dissolution pores. Specifically, on the structural high, where well-developed faults define an open geochemical system, extensive dissolution is observed with only limited precipitation of byproducts (e.g., quartz and feldspar overgrowth). Notably, the dissolution of intergranular calcite cements is more prevalent than that of feldspar grains. Reservoir spaces are dominated by interconnected, poorly-cemented intergranular enlarged pores and intragranular dissolution pores. In contrast, on the downdip slope, where the geochemical system is relatively closed, moderate dissolution of both feldspar and calcite cements occurred concurrently with substantial precipitation of byproducts. There, pore systems consist mainly of inter-crystalline pores and poorly connected dissolution pores, with most dissolution pores being occluded by kaolinite, quartz overgrowth and other dissolution-related byproducts. This study indicates that under progressively closed geochemical conditions, the dissolution capacity of meteoric water infiltrating downward through faults and porous sandstones is markedly weakened. Concurrently, the re-precipitation of dissolved cations within the system is enhanced. These coupled diagenetic processes ultimately control the distribution of high-quality reservoirs in uplifted structural belts.
{"title":"Effects of meteoric water–rock interaction on the quality of the Middle Jurassic reservoirs along the Hongciliang tectonic belt, Yabulai Basin, NW China","authors":"Shuangqi Feng , Hancheng Ji , Liang Chen , Xuegui Jiang , Pengfei Xiang , Yanqing Shi , Chunfu Liao , Ying Liu , Ling Li","doi":"10.1016/j.jseaes.2025.106936","DOIUrl":"10.1016/j.jseaes.2025.106936","url":null,"abstract":"<div><div>In recent years, the penetration of meteoric water through unconformities and porous sandstones, and its subsequent dissolution effects within deep-seated reservoirs, has attracted widespread attention. Assessing whether a diagenetic system is open or closed is crucial for evaluating how dissolution influences reservoir quality. However, for structural uplifts with large-scale, deep-seated faults, how dissolution from meteoric water leaching varies spatially from the structural high to the downdip slope, and the resulting reservoir characteristics, remain poorly understood. To address this, we conducted an integrated analysis of diagenetic mineral assemblages and the associated paragenetic sequence in the Middle Jurassic reservoir of the Hongciliang tectonic belt, Yabulai Basin. Methods included thin-section petrography, scanning electron microscopy (SEM), isotopic testing, X-ray diffraction (XRD), reservoir porosity–permeability measurements, and computerized tomography (CT) scanning. Results demonstrate that the medium- to fine-grained arkoses in the Hongciliang tectonic belt were deposited under similar sedimentary environments. Nevertheless, differential dissolution, coupled with mass transfer and re-precipitation of dissolved materials, results in substantial differences between the structural high and downdip slope. These differences are manifested in the development of dissolution pores, as well as in the types and abundances of authigenic minerals within dissolution pores. Specifically, on the structural high, where well-developed faults define an open geochemical system, extensive dissolution is observed with only limited precipitation of byproducts (e.g., quartz and feldspar overgrowth). Notably, the dissolution of intergranular calcite cements is more prevalent than that of feldspar grains. Reservoir spaces are dominated by interconnected, poorly-cemented intergranular enlarged pores and intragranular dissolution pores. In contrast, on the downdip slope, where the geochemical system is relatively closed, moderate dissolution of both feldspar and calcite cements occurred concurrently with substantial precipitation of byproducts. There, pore systems consist mainly of inter-crystalline pores and poorly connected dissolution pores, with most dissolution pores being occluded by kaolinite, quartz overgrowth and other dissolution-related byproducts. This study indicates that under progressively closed geochemical conditions, the dissolution capacity of meteoric water infiltrating downward through faults and porous sandstones is markedly weakened. Concurrently, the re-precipitation of dissolved cations within the system is enhanced. These coupled diagenetic processes ultimately control the distribution of high-quality reservoirs in uplifted structural belts.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"298 ","pages":"Article 106936"},"PeriodicalIF":2.4,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145842660","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}
Pub Date : 2025-12-22DOI: 10.1016/j.jseaes.2025.106938
Truong Xuan Le , Khin Zaw , Hai Thanh Tran , Sebastien Meffre , Pham Trung Hieu , Nguyen Dinh Luyen , Luong Quang Khang , Dinh Trong Tuong
The Me Xi Au deposit lies within the central Truong Son Belt, which is the largest geological structure in the Indochina Block. This region was primarily shaped by the Ordovician-Silurian (O-S) Caledonian and Permian-Early Triassic (P-T1) Indosinian orogenies. In this study, LA-ICP-MS apatite and zircon ages, along with lead isotopic composition obtained from galena and pyrite at the Me Xi Au deposit using Aqua Regia digestion and LA-ICP-MS techniques have been analysed. The results confirmed that: (1) the porphyritic dolerite yields an apatite U-Pb age of 448 ± 33 Ma. However, considering the stratigraphic constraints, this likely represents an emplacement age of ∼430–415 Ma within the analytical uncertainty range. Combined with the geochemical signatures (e.g., Zr/TiO2 and Ti/V ratios) of an extensional setting and the historical geology, this indicates a post-collision magmatism related to the Caledonian Orogeny between the Truong Son Belt and Kon Tum Massif; (2) the early Au-mineralization event (Stage 2) has predominantly upper-crustal lead sources with Paleozoic model ages. This is possibly linked to the ∼430–415 Ma post-collision dolerite of the Caledonian Orogeny; (3) the late Au-mineralization event (Stage 3) has mixed magmatic-upper crustal lead sources and Mesozoic model ages, possibly marks a metallogenic event during the post-collision phase of the Indosinian Orogeny; (4) host rocks at Me Xi comprising siltstone and sandstone are constrained by a maximum depositional age of ∼580 Ma (i.e., youngest detrital zircon) and the minimum age of ∼430–415 Ma (i.e., ages of dolerite crosscutting metasedimentary rocks). These results highlight the significance of Ordovician-Silurian magmatism in the regional tectonic framework and metallogenic evolution of the central Truong Son Belt.
{"title":"Early Paleozoic magmatism and Au mineralization in the central Truong Son Belt: Insights from geochronology and lead isotope at the Me Xi gold deposit, Vietnam","authors":"Truong Xuan Le , Khin Zaw , Hai Thanh Tran , Sebastien Meffre , Pham Trung Hieu , Nguyen Dinh Luyen , Luong Quang Khang , Dinh Trong Tuong","doi":"10.1016/j.jseaes.2025.106938","DOIUrl":"10.1016/j.jseaes.2025.106938","url":null,"abstract":"<div><div>The Me Xi Au deposit lies within the central Truong Son Belt, which is the largest geological structure in the Indochina Block. This region was primarily shaped by the Ordovician-Silurian (O-S) Caledonian and Permian-Early Triassic (P-T<sub>1</sub>) Indosinian orogenies. In this study, LA-ICP-MS apatite and zircon ages, along with lead isotopic composition obtained from galena and pyrite at the Me Xi Au deposit using Aqua Regia digestion and LA-ICP-MS techniques have been analysed. The results confirmed that: (1) the porphyritic dolerite yields an apatite U-Pb age of 448 ± 33 Ma. However, considering the stratigraphic constraints, this likely represents an emplacement age of ∼430–415 Ma within the analytical uncertainty range. Combined with the geochemical signatures (e.g., Zr/TiO<sub>2</sub> and Ti/V ratios) of an extensional setting and the historical geology, this indicates a post-collision magmatism related to the Caledonian Orogeny between the Truong Son Belt and Kon Tum Massif; (2) the early Au-mineralization event (Stage 2) has predominantly upper-crustal lead sources with Paleozoic model ages. This is possibly linked to the ∼430–415 Ma post-collision dolerite of the Caledonian Orogeny; (3) the late Au-mineralization event (Stage 3) has mixed magmatic-upper crustal lead sources and Mesozoic model ages, possibly marks a metallogenic event during the post-collision phase of the Indosinian Orogeny; (4) host rocks at Me Xi comprising siltstone and sandstone are constrained by a maximum depositional age of ∼580 Ma (i.e., youngest detrital zircon) and the minimum age of ∼430–415 Ma (i.e., ages of dolerite crosscutting metasedimentary rocks). These results highlight the significance of Ordovician-Silurian magmatism in the regional tectonic framework and metallogenic evolution of the central Truong Son Belt.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"298 ","pages":"Article 106938"},"PeriodicalIF":2.4,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145842631","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}
Pub Date : 2025-12-22DOI: 10.1016/j.jseaes.2025.106934
Harsh Limbachiya , Sumer Chopra , Tarun Solanki
A network of broadband seismic stations has been deployed across the Gujarat region in western India, covering diverse geological settings. Microtremor data obtained at these stations are used to characterize the sites through horizontal to vertical spectral ratio (HVSR) analysis. The HVSR curves are modeled to derive 1D shear-wave velocity (VS) profile beneath each site. The fundamental frequency (f0) across the Gujarat varies between 0.2 and 17.7 Hz with values of 0.2–0.5 Hz and 0.9–1.2 Hz observed for sites located on Quaternary and Rann sediments, respectively. Most sites underlain by Tertiary and Cretaceous formations exhibit flat HVSR curves, while Deccan Trap sites show similarly flat responses up to 10 Hz. The VS30, a key parameter for site characterization, varies from 228 to 743 m/s across Gujarat. At sites underlain by Quaternary sediments, the average VS30 is 288 ± 34 m/s. For Tertiary, Jurassic, Cretaceous and Proterozoic formations, the average VS30 values are 413 ± 85 m/s, 478 ± 76 m/s, 435 ± 56 m/s and 680 ± 28 m/s, respectively. In Deccan Traps, an average VS30 of 585 ± 64 m/s is observed. The VS30 values obtained from the HVSR modelling show good agreement with those obtained from active seismic methods such as multi-channel analysis of surface waves (MASW). This study presents the first region-wide site characterization of Gujarat using microtremor data. It demonstrates the efficacy of HVSR-based modeling in capturing geology-controlled variations in site response across a tectonically active and lithologically complex region. The results provide essential inputs for seismic hazard assessment, engineering design, and future microzonation studies in western India.
{"title":"Microtremor-based site characterization for Gujarat broadband seismological network established in an intraplate setting","authors":"Harsh Limbachiya , Sumer Chopra , Tarun Solanki","doi":"10.1016/j.jseaes.2025.106934","DOIUrl":"10.1016/j.jseaes.2025.106934","url":null,"abstract":"<div><div>A network of broadband seismic stations has been deployed across the Gujarat region in western India, covering diverse geological settings. Microtremor data obtained at these stations are used to characterize the sites through horizontal to vertical spectral ratio (HVSR) analysis. The HVSR curves are modeled to derive 1D shear-wave velocity (<em>V<sub>S</sub></em>) profile beneath each site. The fundamental frequency (<em>f<sub>0</sub></em>) across the Gujarat varies between 0.2 and 17.7 Hz with values of 0.2–0.5 Hz and 0.9–1.2 Hz observed for sites located on Quaternary and Rann sediments, respectively. Most sites underlain by Tertiary and Cretaceous formations exhibit flat HVSR curves, while Deccan Trap sites show similarly flat responses up to 10 Hz. The <em>V<sub>S30</sub></em>, a key parameter for site characterization, varies from 228 to 743 m/s across Gujarat. At sites underlain by Quaternary sediments, the average <em>V<sub>S30</sub></em> is 288 ± 34 m/s. For Tertiary, Jurassic, Cretaceous and Proterozoic formations, the average <em>V<sub>S30</sub></em> values are 413 ± 85 m/s, 478 ± 76 m/s, 435 ± 56 m/s and 680 ± 28 m/s, respectively. In Deccan Traps, an average <em>V<sub>S30</sub></em> of 585 ± 64 m/s is observed. The <em>V<sub>S30</sub></em> values obtained from the HVSR modelling show good agreement with those obtained from active seismic methods such as multi-channel analysis of surface waves (MASW). This study presents the first region-wide site characterization of Gujarat using microtremor data. It demonstrates the efficacy of HVSR-based modeling in capturing geology-controlled variations in site response across a tectonically active and lithologically complex region. The results provide essential inputs for seismic hazard assessment, engineering design, and future microzonation studies in western India.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"298 ","pages":"Article 106934"},"PeriodicalIF":2.4,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145842633","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}
Pub Date : 2025-12-22DOI: 10.1016/j.jseaes.2025.106932
Rongqiang Guo , Shijiong Han , Chenggang Cao , Kaizhang Shi , Yurui Yuan , Mingyu Tang , Jinxin Yuan , Yongkun Fang , Yushan Jia
The genesis of the Nalinguolehexi (Naxi) skarn Fe polymetallic deposit, Eastern Kunlun, China, remains poorly constrained. This study presents in-situ LA-ICP-MS trace element and sulfur isotope analyses of pyrite and pyrrhotite to decipher its fluid evolution. Four sulfide generations (Py1, Py2, Po, Py3) were identified. Early pyrite (Py1, Py2) is enriched in Co and Ni (Co/Ni > 1), indicating a hydrothermal origin, whereas late-stage Py3 shows pronounced enrichment in As, Pb, Bi, and Sb. Sulfur isotopes (δ34S = −5.9 ‰ to 8.2 ‰) display a decreasing trend from early (avg. 6.6 ‰) to late generations (avg. −5.3 ‰). Elevated early δ34S values suggest magmatic sulfur mixed with crustal or limestone-derived sulfur. Porous textures in Py3, trace element signatures, and principal component analysis collectively indicate a late-stage fluid boiling event. This boiling increased oxygen fugacity and pH, triggering base metal precipitation and inducing kinetic sulfur isotope fractionation responsible for the negative δ34S values. The Naxi deposit is classified as a typical skarn-type system formed by contact metasomatism between magmatic-hydrothermal fluids and the Dagangou Formation limestone. Fluid cooling and boiling were the pivotal mechanisms controlling metal precipitation and isotopic variation. This study identifies geochemical proxies for boiling in skarn systems, offering critical insights for exploring concealed deposits in the Qimantage belt and similar intracontinental settings.
{"title":"Fluid evolution in the Naxi Fe polymetallic deposit, Eastern Kunlun, China: Insights from in-situ trace element and sulfur isotope compositions of pyrite and pyrrhotite","authors":"Rongqiang Guo , Shijiong Han , Chenggang Cao , Kaizhang Shi , Yurui Yuan , Mingyu Tang , Jinxin Yuan , Yongkun Fang , Yushan Jia","doi":"10.1016/j.jseaes.2025.106932","DOIUrl":"10.1016/j.jseaes.2025.106932","url":null,"abstract":"<div><div>The genesis of the Nalinguolehexi (Naxi) skarn Fe polymetallic deposit, Eastern Kunlun, China, remains poorly constrained. This study presents in-situ LA-ICP-MS trace element and sulfur isotope analyses of pyrite and pyrrhotite to decipher its fluid evolution. Four sulfide generations (Py1, Py2, Po, Py3) were identified. Early pyrite (Py1, Py2) is enriched in Co and Ni (Co/Ni > 1), indicating a hydrothermal origin, whereas late-stage Py3 shows pronounced enrichment in As, Pb, Bi, and Sb. Sulfur isotopes (δ<sup>34</sup>S = −5.9 ‰ to 8.2 ‰) display a decreasing trend from early (avg. 6.6 ‰) to late generations (avg. −5.3 ‰). Elevated early δ<sup>34</sup>S values suggest magmatic sulfur mixed with crustal or limestone-derived sulfur. Porous textures in Py3, trace element signatures, and principal component analysis collectively indicate a late-stage fluid boiling event. This boiling increased oxygen fugacity and pH, triggering base metal precipitation and inducing kinetic sulfur isotope fractionation responsible for the negative δ<sup>34</sup>S values. The Naxi deposit is classified as a typical skarn-type system formed by contact metasomatism between magmatic-hydrothermal fluids and the Dagangou Formation limestone. Fluid cooling and boiling were the pivotal mechanisms controlling metal precipitation and isotopic variation. This study identifies geochemical proxies for boiling in skarn systems, offering critical insights for exploring concealed deposits in the Qimantage belt and similar intracontinental settings.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"298 ","pages":"Article 106932"},"PeriodicalIF":2.4,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145842642","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}
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