Journal of Asian Earth Sciences最新文献

{"title":"Origin and distribution of Cambrian to Ordovician weathering crust dolostone reservoirs in the Ordos Basin, NW China","authors":"Chun Wu ,&nbsp;Bo Liu ,&nbsp;Liubin Wei ,&nbsp;Xinshe Liu ,&nbsp;Jin Lai ,&nbsp;Kaibo Shi ,&nbsp;Feifan Lu ,&nbsp;Qing He ,&nbsp;Senran Chen","doi":"10.1016/j.jseaes.2024.106476","DOIUrl":"10.1016/j.jseaes.2024.106476","url":null,"abstract":"<div><div>Recent advances in natural gas exploration have led to notable breakthroughs in weathering crust dolostone reservoirs. The Huaiyuan Epeirogeny, which occurred from the Cambrian to Ordovician periods, contributed to the formation of weathering crust dolostones in the southwestern Ordos Basin, NW China. A combination of core analysis, thin section microscopy, scanning electron microscopy, and conventional and image logs has been employed to characterize the karst features present in these reservoirs. Lithologies are classified based on crystalline size, with pore spaces including isolated pores, cavities, and fractures. Five distinct image log assemblages have been identified to describe the karst features. Vertically, the weathering crust is divided into four zones: the surface karst zone, the vertical vadose zone, the horizontal underflow zone, and the deep slow flow zone. These vertical zonations are predicted using image logs and conventional well logs. The majority of gas-producing intervals are located in the vertical vadose zone. The cavity and fracture systems in the surface zone are distributed locally, while fractures in the vertical vadose zone, especially those connected to vugs, considerably enhance hydrocarbon productivity. Based on these findings, a karstification model for the weathering crust has been developed, offering valuable insights into the karst features of these reservoirs. This research provides a reference for future oil and gas exploration in weathering crust dolostone reservoirs in similar basins.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"280 ","pages":"Article 106476"},"PeriodicalIF":2.7,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143092058","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":"Petrological and geochemical characteristics of Ordovician cherts in the Qasim Formation, NW Saudi Arabia: Understanding the roles of biogenic and volcanic activities","authors":"Abdulwahab M. Bello ,&nbsp;Abduljamiu O. Amao ,&nbsp;Ardiansyah I. Koeshidayatullah ,&nbsp;Mahmoud Alnazghah ,&nbsp;Mohammad A. Alrowaie ,&nbsp;Adhipa Herlambang ,&nbsp;Khalid Al-Ramadan","doi":"10.1016/j.jseaes.2024.106483","DOIUrl":"10.1016/j.jseaes.2024.106483","url":null,"abstract":"<div><div>The Upper Ordovician Qasim Formation features bedded cherts with mudstone interbeds, which are overlain by Tertiary volcanic rocks. The origin and formation conditions of the cherts are almost completely unknown. To address these, this study employed thin-section petrography, XRF analysis, REE geochemistry, SEM analysis, and stable oxygen isotopes. Results of the study indicate that the cherts are primarily biogenic, derived from siliceous sponges, with contributions from terrestrial and river sources. Silica from marine upwelling and terrestrial sources enhanced biogenic activity, leading to the formation of the chert. Ratios of Si/(Si + Al + Fe) and Al/(Al + Fe + Mn) support a biogenic silica origin, while REEs suggest formation under oxic marine conditions (Ce/Ce* anomaly 0.3–1.0, avg. 0.7). The cherts also show an average Y/Ho value of 33.3, indicating marine influence with freshwater input. Diagenesis played a vital role in the formation of the cherts, with microcrystalline quartz replacing carbonate bioclasts and subsequently partly recrystallizing into blocky mega-quartz near chert-basalt contact. The microquartz cherts have δ ¹⁸O values of 26.7 to 33.7 ‰ (± 0.6 ‰), corresponding to formation temperatures of approximately 14 to 45 °C (avg. 38 °C; ±3 °C), whereas the mega-quartz chert has a δ ¹⁸O of 20.4 ‰ (±0.6 ‰), reflecting a formation temperature of approximately 115 ± 5 °C). These oxygen isotope values and temperatures reveal that the microquartz chert formed in cooler, shallow marine conditions, while the megaquartz chert was affected by a significant thermal event at the contact with the Tertiary basalt emplaced over the chert layers. These findings provide insights into paleoenvironmental conditions, thermal history, and the impact of later volcanic activity on chert recrystallization.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"280 ","pages":"Article 106483"},"PeriodicalIF":2.7,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143097055","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":"Late Quaternary vertical throw rates along the Gyaring Co fault in central Tibet","authors":"Duo Wang ,&nbsp;Lichun Chen ,&nbsp;Hong Chang ,&nbsp;Shugang Kang ,&nbsp;Yongshun Jia ,&nbsp;Jinhua Du ,&nbsp;Fei Han ,&nbsp;Yanbao Li ,&nbsp;Gongming Yin ,&nbsp;Wenjun Zheng ,&nbsp;Xulong Wang","doi":"10.1016/j.jseaes.2024.106484","DOIUrl":"10.1016/j.jseaes.2024.106484","url":null,"abstract":"<div><div>Although normal components along the strike-slip faults have been widely found in central Tibet, poorly constrained vertical rates impede the recognition of their formation mechanism and tectonic implications. Herein, we systematically obtained spatial distribution of well-defined vertical throw rates along the Gyaring Co fault (GCF) using high-precision unmanned aerial vehicle topographic data and optically stimulated luminescence dating on oblique faulted fans and shorelines. Our integrated data indicated a southeastward decrease in Late Quaternary vertical throw rates from ∼0.12 to 0.05 mm/yr along the GCF. The vertical and horizontal movements of the GCF have shared similar rate gradient and have been partitioned with general steady ratios of 5–7.5 % since the Late Quaternary, which suggests that at least half of the motion on the GCF is accommodated by the southern linked Xainza rift. The vertical throws of the GCF are compatible with the conjugated Wuru Co fault, other strike-slip faults, and grabens in central Tibet but are tenfold slower than those of the southern linked rifts. Thus, our results indicate that the eastward motion of the conjugate strike-slip fault system could probably contribute to normal throws along the GCF. The disperse and slow normal faulting within the conjugate zones may initiated at the Middle Miocene as the secondary structures of the conjugate system in central Tibet, kinematically different from the considerably strong and independent southern linked rifts.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"280 ","pages":"Article 106484"},"PeriodicalIF":2.7,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143097054","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":"Linking hydrothermal He-CO2 degassing to regional seismicity in the volcanically and tectonically active Tengchong block, southeastern Tibetan Plateau","authors":"Haoying Zhang ,&nbsp;Wei Liu ,&nbsp;Hui Nai ,&nbsp;Chuanqiang Sun ,&nbsp;Maoliang Zhang","doi":"10.1016/j.jseaes.2024.106478","DOIUrl":"10.1016/j.jseaes.2024.106478","url":null,"abstract":"<div><div>The volcanically and tectonically active regions are manifest by the co-existence of hydrothermal degassing and seismic activities, but the potential links between them remain enigmatic. Here, we present flux estimates for hydrothermal He and CO₂ from the Tengchong block, southeastern Tibetan Plateau, to constrain the role of magmatic fluids in triggering earthquakes. The He-CO₂ systematics reveal significant anomalies of mantle He and CO₂ degassing in localized volcanically active regions (VAR) that are superposed upon a broader tectonically active region (TAR).This correlates well with geophysically detected melts at crustal depths and suggests focused supply of magmatic fluids to hydrothermal system. Higher fluxes of mantle He [(1.08 ± 0.84) × 10¹⁰ atoms m⁻² s⁻¹] and CO₂ [(1.29 ± 1.00) × 10⁴ mol km⁻² yr⁻¹] of magmatic origins concentrate in the VAR rather than the TAR [mantle He and CO₂ flux = (0.26 ± 0.16) × 10¹⁰ atoms m⁻² s⁻¹ and (0.32 ± 0.19) × 10⁴ mol km⁻² yr⁻¹, respectively]. Spatially, high magmatic He-CO₂ fluxes in the VAR correspond well with several earthquake swarms and deep low-frequency earthquakes, while the TAR with much lower fluxes of magmatic fluids generally hosts tectonic earthquakes that align along active faults. These observations offer plausible evidence for the crucial role of magmatic fluids in causing overpressure in seismogenic zone beneath the VAR, which differs from stress-dominated earthquake nucleation in the TAR, suggesting the interplay between magmatic fluids and tectonic faulting in driving regional seismicity.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"280 ","pages":"Article 106478"},"PeriodicalIF":2.7,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143092061","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":"Provenance of Neoarchaean metagreywackes on the western margin of the Western Dharwar Craton, South India: Implications for Madagascar − Western Dharwar Craton connection","authors":"Venkatraman S. Hegde ,&nbsp;Hartwig E. Frimmel ,&nbsp;N. Rebeun ,&nbsp;Asim Ranjan Pratihari ,&nbsp;G. Shalini","doi":"10.1016/j.jseaes.2024.106474","DOIUrl":"10.1016/j.jseaes.2024.106474","url":null,"abstract":"<div><div>Neoarchaean, low-grade metamorphic greywackes of the Ranibennur Formation of Chitradurga Group of Dharwar Supergroup, from the Western Dharwar Craton (WDC) were studied to understand their provenance. The metagreywackes consist of detrital quartz, feldspar and volcanic and plutonic lithic fragments in a chlorite-sericite-dominated matrix. They have low to moderate chemical indices of alteration (CIA) (50 to 60.4). The metagreywackes are characterized by fractionated light rare earth element (LREE) and moderately fractionated heavy rare earth element (HREE) patterns (Gd_N/Yb_N 1.0–3.97) and negative Eu/Eu* anomaly (∼0.79). The detrital zircon ages indicate an overwhelming contribution from 2.56 − 2.57 Ga and 2.67–2.68 Ga sources. Integration of their petrographic and geochemical characteristics suggests a provenance composed of a mix of recycled and arc-derived sediments. A four component mixing model indicated ∼55 % of tonalitic-trondhjemitic to granodioritic; 17 to 20 % of granitic, 20–22 % mafic volcanic and 3–5 % ultramafic rocks constituted the provenance composition. The rarity of igneous 2.67–2.68 Ga source rocks in the Dharwar Craton and the presence of such rocks in the eastern part of Madagascar suggest that the detrital zircon grains of that age were mainly derived from eastern Madagascar. This would imply that eastern Madagascar was part of the Dharwar Craton.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"280 ","pages":"Article 106474"},"PeriodicalIF":2.7,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143136399","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":"Structural and lithological controls on the evolution of ore-forming fluids during the formation of the Chaihulanzi gold deposit, NE China","authors":"Zhao Liu ,&nbsp;Lin Yang ,&nbsp;Qingfei Wang ,&nbsp;Chao Li ,&nbsp;Kexin Zhao ,&nbsp;Chuan Xu ,&nbsp;Dong Xu ,&nbsp;Zhuang Zhang ,&nbsp;Kang Wang","doi":"10.1016/j.jseaes.2024.106473","DOIUrl":"10.1016/j.jseaes.2024.106473","url":null,"abstract":"<div><div>The Chaihulanzi gold deposit, located along the northern margin of the North China Craton, is an example of detecting the controls on the complexity of orogenic gold systems. This deposit consists of a series of gold lodes hosted in graphite-schist, gneiss, and porphyrite and is controlled by NW- to NWW-directed faults. The graphite-schist-hosted gold lodes contain pyrite-arsenopyrite-dominated polymetallic sulfides, whereas the gneiss- and porphyrite-hosted lodes are characterized by pyrite-pyrrhotite-dominated polymetallic sulfides. Despite variations in ore-minerals, these lodes exhibit similar quartz-sericite ± carbonate-chlorite alteration. In the dilatational faults, the <em>δ</em>³⁴S values of pyrite from graphite-schist-hosted lodes from + 0.4 to + 6.5 ‰, whereas pyrite from gneiss-hosted lodes have <em>δ</em>³⁴S values ranging from −3.5 to + 8.5 ‰. In the compressional faults, pyrite from porphyrite-hosted lodes shows <em>δ</em>³⁴S values between + 2.3 to + 4.4 ‰. The broader range of <em>δ</em>³⁴S values from dilatational-lodes compared to compressional-lodes can be attributed to varying fluid-rock interactions and fluid pressure fluctuations. The contrasting ore minerals and sulfur isotope are linked to the interaction of ore-forming fluids with different host rocks in complex structural and lithological settings. Specifically, the relatively positive <em>δ</em>³⁴S in pyrite from graphite-schist-hosted lodes may result from the fluid reduction due to reaction with graphite-schist. The Pb isotope of pyrite with ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb ratios of 18.51–22.13, 15.69–16.54, and 37.92–43.59, respectively, support the hypothesis of Pb contamination of the host rocks. This study underscores the detailed influence of structural settings and lithologies on the complexity of ore-forming fluid compositions and provides valuable insights for guiding regional exploration.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"280 ","pages":"Article 106473"},"PeriodicalIF":2.7,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143136362","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":"Diverse geodynamic settings of the Egyptian ophiolites: Geochemical insights from Wadi Ghadir and Gabal Abu Dahr","authors":"Mohammed El-Bialy ,&nbsp;Basem Zoheir ,&nbsp;Aliaa Diab ,&nbsp;Mark Feigenson ,&nbsp;Amr Abdelnasser","doi":"10.1016/j.jseaes.2024.106480","DOIUrl":"10.1016/j.jseaes.2024.106480","url":null,"abstract":"<div><div>In the context of the ongoing debate on the genetic aspects of Egyptian ophiolites, understanding the geodynamic setting of significant ophiolitic complexes is crucial. Here, we investigate the Wadi Ghadir (WG) and Gabal Abu Dahr (AD) ophiolites to elucidate their tectonic setting and evolution. Combining whole-rock trace element geochemical data of crustal and mantle section rocks with mineral chemistry analyses of relict clinopyroxene and Cr-spinel, we delineate the geochemical signatures indicative of their tectonic setting. The WG represents a nearly complete ophiolite sequence, while the AD complex is a dismembered ophiolite nappe encompassing serpentinized peridotite, variably sheared metagabbro, and mélange matrix. The trace element patterns of the crustal section rocks in both ophiolites exhibit enrichments in LILE and depletions in HFSE, suggesting formation in a supra-subduction zone (SSZ). The low Ti contents and fractionated chondrite-normalized REE patterns of clinopyroxenes from both studied ophiolites further support the subduction-induced characteristics. The highly elevated Cr# of Cr-spinel in the WG and AD serpentinites, alongside their high Mg# and low TiO2 contents, resemble those of the forearc basalts and boninites, indicative of extensive melt extraction. Despite the shared features of progressive evolution to boninite-similar geochemistry, the AD ophiolite is deemed unlikely to have experienced the MORB or backarc environments. Conversely, the WG ophiolite has geochemical signatures inferring transitioning from back-arc MORB-like lithosphere to the SSZ setting. Although originating from distinct geodynamic settings, these ophiolites can be conceptualized as representing a Tonian-Cryogenian sub-arc lithosphere (∼730–700 Ma) in the Egyptian Eastern Desert, showcasing varied responses to subduction-related processes.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"280 ","pages":"Article 106480"},"PeriodicalIF":2.7,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143136398","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":"Petrogenesis and tectonic implications of blueschist-facies garnet-mica schist in the Dabie orogenic belt, central China","authors":"Juan Wang ,&nbsp;Jun Chen ,&nbsp;Yonghong Shi ,&nbsp;Nanfei Cheng ,&nbsp;Guoxin Tang ,&nbsp;Chunlei Peng ,&nbsp;Jiankang Tang ,&nbsp;Junjie Li","doi":"10.1016/j.jseaes.2024.106482","DOIUrl":"10.1016/j.jseaes.2024.106482","url":null,"abstract":"<div><div>The Dabie orogenic belt (DOB) in central China is renowned for studies of ultrahigh-pressure metamorphism due to deep continental subduction. However, relatively high-pressure and low-temperature (HP/LT) metamorphism in the DOB is poorly understood. To provide constraints on such metamorphism, we carried out a detailed petrological investigation on a garnet-mica schist from the Central Dabie metamorphic zone. Thermodynamic calculation, based on petrographic and mineral chemical data, revealed three distinct metamorphic episodes (i.e., M1, M2, and M3) with pressures and temperatures of 1.98 ± 0.01 GPa/457 ± 3°C, 1.93 ± 0.06 GPa/515 ± 19°C, and 1.51 ± 0.19 GPa/525 ± 14°C, respectively, which are generally under the HP/LT conditions of blueschist-facies metamorphism. The resulting clockwise <em>P–T</em> path reflects isobaric heating (M1 → M2) and isothermal decompression (M2 → M3), suggesting termination of the slab subduction and subsequent rapid uplift, respectively. Furthermore, zircon analysis yielded two distinct groups. Zrn-I represents the core of the zircons and exhibits an inherited magmatic origin, with a Neoproterozoic age range of 827–682 Ma; Zrn-II corresponds to the rim of the zircons and has a metamorphic origin, with an age of 197 ± 5 Ma, correlating with the M3 episode. These results, combined with previous studies, suggest that the transition from shallow warm subduction to deep cold subduction in the DOB may occur at a depths of 35–65 km in a low geothermal gradient environment, and the final exhumation of the orogenic belt to the surface may originate from the large-scale extension and deformation in eastern China.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"280 ","pages":"Article 106482"},"PeriodicalIF":2.7,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143136361","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":"Petrogenesis and geodynamic implications of gabbroic diorites of the early Paleozoic Mijiashan ophiolite in the eastern North Qilian Orogenic Belt, NW China","authors":"Jiao-Long Zhao ,&nbsp;Liang Liu ,&nbsp;Qing-Yan Tang ,&nbsp;Jin-Rong Wang ,&nbsp;Zhen-Xi Yang ,&nbsp;Pei-Qing Hu ,&nbsp;Xin-Wei Zhai ,&nbsp;Saniye Abdereyimu ,&nbsp;Zi-Han Dang","doi":"10.1016/j.jseaes.2024.106481","DOIUrl":"10.1016/j.jseaes.2024.106481","url":null,"abstract":"<div><div>The early Paleozoic North Qilian Orogenic Belt (NQOB) records a complex history, from early oceanic subduction and back-arc extension to the eventual closure of the ocean and continental collision. The tectonic nature of the back-arc basin and its evolution are debated. The Mijiashan (MJS) ophiolite in the eastern NQOB is thought to represent remnants of the North Qilian back-arc, and consists mainly of a crustal sequence of basalts, plagiogranites, and gabbroic intrusions. A fine-grained gabbroic diorite intrusion has recently been identified in this crustal sequence. We present new zircon U–Pb ages and bulk-rock chemical and Sr–Nd isotopic data for these rocks. Zircon grains from the gabbroic diorite yield a U–Pb age of 510 Ma, which is taken to be the crystallization age of the rocks, consistent with the field relationship. The diorite is tholeiitic in composition, enriched in Cs, Ba, Sr, and Pb, and depleted in Nb, Ta, Th, and Rb on a primitive-mantle-normalized trace element spider diagram. It has low total rare earth element (REE) contents and yields chondrite-normalized rare earth element patterns depleted in light REEs. The MJS gabbroic diorite has depleted isotopic compositions [whole-rock ε_Nd(t) = +4.96 to + 5.25; initial ⁸⁷Sr/⁸⁶Sr ratio = 0.7055–0.7066]. These geochemical and isotopic characteristics suggest that these rocks were formed from melts that were derived from partial melting of residual, extremely refractory, hydrated mantle peridotite. This mantle wedge source had previously experienced the extraction of MORB-type melts and was subsequently metasomatized primarily by subduction-derived fluids, with minimal contributions from seafloor sediment components. The gabbroic diorite of the MJS ophiolite was formed in an intracontinental back-arc setting and represents the earliest identified magmatic record of the initiation of arc rifting in a supra-subduction zone environment in response to rollback of the northward-subducting North Qilian oceanic lithosphere.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"280 ","pages":"Article 106481"},"PeriodicalIF":2.7,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143136397","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":"Dominant wind patterns shaping grain-size records at IODP Site U1430 in the East (Japan) Sea since the early Pleistocene: Northwesterly surface winds vs. upper westerlies","authors":"Jun-Ho Jang ,&nbsp;Jang-Jun Bahk ,&nbsp;Dong Eun Lee","doi":"10.1016/j.jseaes.2024.106479","DOIUrl":"10.1016/j.jseaes.2024.106479","url":null,"abstract":"<div><div>Grain-size records of detrital components at IODP Site U1430 in the East (Japan) Sea, spanning the last 2.3 million years, are examined to understand how variations in the intensity of the East Asian Winter Monsoon influenced these records through two distinct dust-transporting wind patterns: low-level northwesterly winter monsoon winds and upper-level westerlies. By applying end-member (EM) modelling to grain-size distributions, we identified five EMs corresponding to fine-mode dust carried by upper-level westerlies (EM1), coarse-mode dust transported by northwesterly surface winds (EM2), and marine tephra of varying modes (EM3, EM4, and EM5). To isolate the dust components, we excluded marine tephra contributions and developed a dust-size distribution model based solely on EM1 and EM2. The mean size variations of this modeled dust at Site U1430 exhibited strong consistency in both cyclicity and amplitude, with similar stacked size records from the Chinese Loess Plateau (CLP). Given that the CLP size records near the source deserts were primarily influenced by northwesterly surface winds, the synchronization between these records and those from Site U1430 suggests that the records from Site U1430 were also predominantly governed by changes in the intensity of northwesterly surface winds rather than upper westerlies. The spatial variations in size records from the loess sections across the CLP, along with modern dust size observations, imply that the vertical and lateral sorting of dust during uplift and downwind transport likely contributed to the smaller dust sizes recorded at Site U1430.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"280 ","pages":"Article 106479"},"PeriodicalIF":2.7,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143097106","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}