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Journal of Asian earth sciences
Elsevier Science Ltd.
Journal of Asian earth sciences

Elsevier Science Ltd.

1367-9120

Journal of Asian earth sciences/Journal Journal of Asian earth sciencesISTPSCIAHCI
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    U-Pb age and Lu-Hf isotopic compositions of zircon from tuff layers of the late Permian-Early Triassic sedimentary succession in the western Yangtze Block, SW China: Implications for the tectonic evolution and Impact of episodic volcanism on biotic recovery

    Chuan, MaoshanPan, JiangtaoWu, LiangLi, Dezong...
    1.1-1.19页
    查看更多>>摘要:The Zhaotong Basin, located at the southwestern margin of the Yangtze Block, is characterized by multiple layers of sedimentary tuffs. However, the tectonic background of tuffs, the timing of episodic volcanism marked by these tuffs, and the relationship between volcanism and biotic recovery remain controversial. In this study, we integrate petrography with zircon U-Pb and Lu-Hf isotope analyses on five tuff layers bracketing the Permian-Triassic boundary. The zircon U-Pb ages of these tuff layers were determined to be 258.9 +/- 0.7 Ma, 254.9 +/- 0.6 Ma, 250.0 +/- 2.8 Ma, 247.1 +/- 1.2 Ma, and 247.2 +/- 0.74 Ma. Among these, the age of 247.2 +/- 0.74 Ma is proposed as a geochronological marker for the Olenekian-Anisian boundary. Geochemical and Lu-Hf isotope data from the Xuanwei Formation indicate that the earliest tuff layer (258.9 +/- 0.7 Ma) originated from acidic volcanism associated with Emeishan basalts. In contrast, the late tuff layer (254.9 +/- 0.6 Ma) corresponds to the onset of the closure of the Paleo-Tethys Ocean subduction, with volcanism persisting into the Middle Triassic (247.2 +/- 0.74 Ma). Episodic volcanism, as evidenced by the five tuff layers, was temporally coupled with the biocrisis that spanned from the Guadalupian (ca. 260 Ma) to the Anisian (247 Ma). The distinctive epsilon(Hf)(t) values reveal substantial crustal contributions to the magmatic systems throughout the volcanic episodes. These findings indicate that recurrent volcanic activity likely contributed to cyclic environmental perturbations and subsequent delays in biotic recovery spanning > 13 Myr.

    Late pleistocene erosion rates of Gushan mountain, Southern Shanxi Rift, North China: evidence from cosmogenic 10Be and 26Al

    Yan, JiyuanLiang, XiaHu, JianminGong, Wangbin...
    1.1-1.9页
    查看更多>>摘要:Erosion serves as a critical link connecting various geological factors that shape landforms, making the quantitative studies of erosion rates of great significance for understanding landscape evolution. In this paper, we first quantified the bedrock erosion rates of the Gushan Mountain in the southern Shanxi Rift, using in-situ produced cosmogenic 10Be and 26Al. The results show that the minimum exposure ages range from 115.4 f 7.2 ka to 26.5 f 1.7 ka, with erosion rates varying between 5.2 f 0.3 mm/ka and 23.6 f 1.5 mm/ka. Ridge samples exhibit erosion rates approximately twice as high as summit samples, suggesting spatial variability in erosion processes and significant influences of topygraphy. The erosion rates of the Gushan Mountain are significantly lower than the basin erosion rates in the Taihang Mountains, suggesting landscape disequilibrium. These rates are comparable to denudation rates derived from low-temperature thermochronology, pointing to a long-term slowpaced landscape evolution of the Gushan Mountain. However, they are significantly lower than denudation rates in adjacent mountains (e.g., Taihang and Zhongtiao Mountains), highlighting the dominant role of tectonic activities in controlling erosion. The differential tectonic activities between the E'mei Platform (hosting Gushan Mountain) and the surrounding mountains of the Shanxi Rift has contributed to observed spatial variation in erosion rates. Notably, the uplift of the E'mei Platform during the Late Pleistocene had a negligible impact on the erosion of the Gushan Mountain.

    Mud volcanoes and microbial communities: Unraveling the mysteries of formation, features, and occurrence

    Rajendran, Senthil KumarKoner, SuprokashHussain, BashirTsai, Hsin-Chi...
    1.1-1.14页
    查看更多>>摘要:Over two thousand mud volcanoes have been documented worldwide, predominantly forming in geologically active regions characterized by rapid sedimentation, recent magmatic activity, and compressional tectonics. These features originate from gravitative instability and fluid overpressure, which induce hydrofracturing of impermeable strata, allowing the release of water, gas, and sediments to the surface. As a result, mud volcanoes occur across a range of tectonic and sedimentary settings, including active margins, accretionary complexes, thrust belts, and deep sedimentary basins. They are generally classified as either submarine or terrestrial mud volcanoes, with the former typically associated with tectonic deformation and the later with sediment accumulation in continental settings. Beyond their geological significance, mud volcanoes contribute substantially to global geochemical and biogeochemical processes, influencing methane production and consumption, nutrient cycling, and organic matter transformation. Additionally, microbial communities are essential in the formation and maintenance of mud volcano structures by contributing to the biomineralization of carbonates and sulfates. The microbial communities found in different mud volcanoes are diverse, and their composition can vary based on location, depth, and geochemical conditions. Moreover, these microbial communities have evolved to utilize diverse sources of energy, including hydrogen, methane, and sulfur, to facilitate metabolic processes. This review summarizes the current insights into the formation, distribution, and environmental constraints of mud volcanoes, while highlighting the ecological relevance and metabolic capabilities of associated microbial communities based on metagenomics data to support interdisciplinary research into geobiological interactions in extreme ecosystems.

    Evolution of deep water circulation in the South China Sea since 32 million years ago

    Huang, Hao-WeiChen, Chih-HuaLiu, ZhifeiHuang, Kuo-Fang...
    1.1-1.13页
    查看更多>>摘要:The closure of the Indonesian Gateway (IG)(1) has played a pivotal role in influencing interocean circulation, notably affecting the Indonesian Throughflow (ITF) and altering climate patterns in Southeast Asia. However, there remains controversy regarding the timing of IG closure and its impacts on climate changes. In this study, we reconstructed Nd isotope (epsilon(Nd)) time series to observe the evolution of South China Sea (SCS) deep water over the past 32 Ma from core sediments at northern SCS and to explore the deep water connection between Indian Ocean and SCS before the fully IG closure.The epsilon(Nd) time series of SCS deep water and benthic delta C-13 composition exhibits a remarkably consistent trend with North Indian Deep Water (NIDW) from 12 to 7 Ma, indicating that NIDW once served as a potential source. This feature implies a deep-water connection between the Indian Ocean and SCS deep water during this period. The observed epsilon(Nd) increases in SCS deep water during key intervals, such as similar to 11, similar to 16, and similar to 25 Ma, likely link to a reduced contribution of LCDW to SCS deep water. Moreover, the Luzon Strait sill became the sole deep-water pathway into the SCS after IG closure. This restriction may have limited LCDW inflow, potentially intensifying its impacts on SCS deep water, as the LCDW contribution to the SCS has been linked to deep SCS carbon reservoirs. Future studies on high-resolution epsilon(Nd) records in SCS are necessary to explore the timing and climatic implications of this tectonic transition.

    Origin and accumulation model of ultra-deep marine natural gas in the Shuntuoguole low Uplift of the Tarim Basin, NW China

    Peng, WeilongLiu, QuanyouMa, YongshengDeng, Shang...
    1.1-1.13页
    查看更多>>摘要:The Tarim Basin, with its relatively low level of exploration, is one of China's largest superimposed petroliferous basins. Recent exploration advancements in the Shunbei-Shunnan area highlight the significant potential for ultra-deep marine natural gas. However, uncertainties surrounding the origin, alteration, and accumulation models of ultra-deep marine natural gas have greatly hindered future hydrocarbon exploration. This study systematically analyzes the geochemical characteristics and genesis of ultra-deep marine natural gas in the Shunbei-Shunnan area. Results indicate that the natural gas in this region comprises both primary and oil-cracking gases. Specifically, the Shunbei area's natural gas is primarily oil-associated, dominated by primary cracking gas with minor contributions from oil-cracking gas, whereas the Shunnan area's natural gas is predominantly oil-cracking gas. The maturity of marine natural gas varies, being higher near the Manjiaer Depression and relatively lower farther away. A sequential distribution of highly mature dry gas, condensate oil and gas, volatile oil, and light oil, accompanied by a gradual decrease in gas-oil ratio, is observed with increasing distance from the Manjiaer Depression. The marine natural gas in the Shunbei-Shunnan area has undergone various alterations, including cracking, thermochemical sulfate reduction, and hydrothermal fluid alteration. Hydrocarbon alteration is more pronounced in the Shunnan area than in the Shunbei area. The active period of strike-slip faults in the Shunbei-Shunnan area coincides with the major hydrocarbon generation and expulsion phases of the source rock. These strike-slip faults serve as critical conduits for hydrocarbon migration, enabling oil and gas to migrate vertically into the middle and upper Ordovician reservoirs, where they form the primary reservoir spaces for accumulation.

    The temporal and spatial evolution of ore-forming fluids during the formation of the Dulong deposit, Southwest China: Linkage with in mineralization

    Fu, JieyongXu, JingZhao, TaipingLi, Jiadai...
    1.1-1.18页
    查看更多>>摘要:The Dulong deposit is a major cassiterite-sulfide skarn deposit in Southwest China, hosting significant In resources (7,000t). Although the occurrence of In has been studied in detail, its spatiotemporal distribution and controlling factors remain poorly understood. This study therefore systematically analyzes fluid inclusions, chlorite geochemistry, and combined with published In contents from sphalerite to comprehensively examine ore-forming fluid evolution and its impact on In mineralization. The fluid inclusions data show that S-type, Ltype, and V-type can be recognized at Dulong. The S-type inclusions predominantly occur in pyroxene from prograde stage and coexist with L-type inclusions, suggesting that fluid boiling occurred. The homogenization temperature and salinity of fluids show a significant decrease from prograde stage (468-560 degrees C, 44.7-49.6 % NaCleqv) to retrograde stage (365-375 degrees C, 3.1-3.7 % NaCleqv), indicating potential mixing with meteoric waters. From retrograde to sulfide stage, both temperature and salinity decrease slightly (from 365-375 degrees C to 210-365 degrees C, and 3.1 %-3.7 % NaCleqvto 0.3 %-2.6 % NaCleqv, respectively), inferring that fluid cooling probably was the key factor for sulfide precipitation and associated In enrichment. The chlorite results show that, from bottom to top of the open pit, this variation in trace element concentrations is dominantly related to the decrease in temperature that occurs during the migration of hydrothermal fluid. The fluid temperatures correlate with increased In concentrations in sphalerite, suggesting temperature controls In enrichment. Additionally, the Ti/Sr ratio in chlorite indicate the possible hydrothermal center at the bottom of the Manjiazhai ore block (approximately 1152 m-depth), implying that the Dulong deposit is probably a distal skarn deposit.

    Petrogenesis of rodingite in the Ngamring massif, Xigaze ophiolite (Southern Tibet): Implications for the evolution of the Neo-Tethys Ocean

    Ou, Gui-FangLiu, Zhong'aoDuan, Wen-YongSun, Guang-Ming...
    1.1-1.16页
    查看更多>>摘要:Rodingites, although volumetrically minor, are integral to the Yarlung Zangbo ophiolites in southern Tibet. However, their tectonic setting, protolith, petrogenesis, and fluid sources remain incompletely understood. This study focuses on rodingites from the Ngamring massif of the Xigaze ophiolite, central Yarlung Zangbo Suture Zone (YZSZ), integrating petrology, mineral and whole-rock geochemistry, and phase equilibrium modeling. The rodingites are structurally heterogeneous and classified into type IA and IB, both featuring metasomatic assemblages of prehnite, chlorite, garnet, and salitic clinopyroxene. Phase equilibrium modeling constrains their formation to low pressure-temperature conditions (<4 kbar and 200-290 degrees C), while relict magmatic clinopyroxenes with high Mg# values [73-87; Mg# = MgO/(MgO + FeO), with all measured iron considered as FeO] suggest a gabbroic protolith crystallized at similar to 6.0-7.4 kbar. Both rodingites types display rare earth and multi-element patterns similar to normal mid-ocean ridge basalt (MORB), comparable to other MORB-like rodingites within the Xigaze ophiolite. The host peridotites show trace-element features characteristic of abyssal peridotites, representing residues after similar to 7-14 % spinel-facies melting of a depleted MORB mantle-like source. The rodingites have variable Sr-87/Sr-86 ratios (0.7036-0.7054) and MORB-like epsilon Nd(t) values (7.3-8.6), suggesting interactions between MOR-derived gabbroic protoliths and serpentinizing fluids derived from the peridotite. Given the presence of metamorphic soles with MORB-type protoliths and both MORB-like and supra-subduction zone magmatic rocks in the YZSZ, it is suggested that the ophiolites likely originated in a MOR environment before evolving into a supra-subduction zone setting as the Neo-Tethys ridge transitioned into an infant subduction system.

    Structural geometry and folding style in the North Dezful Embayment and Abadan Plain, Zagros Fold and Thrust Belt, SW Iran

    Taghavi, AliHajialibeigi, HosseinFard, Iraj AbdollahiMouthereau, Frederic...
    1.1-1.16页
    查看更多>>摘要:The structural geometry within the fold and thrust belts is of particular significance. Consequently, a balanced regional cross-section based on surface, seismic, and subsurface data has been constructed with 236 km lenght perpendicular to the trend of folded strucutres axies in the North Dezful Embayment and the Abadan Plain in the Zagros Fold and Thrust Belt. The cross-section is divided into three districts.The geological structural crosssection passes through the Zagros Simply Folded Belt (the NE and SW Dezful Embayment districts) and the Mesopotamian foreland basin (the Abadan Plain district). This cross-section allowed to study the geometry of the thrust and fold structures vertically and horizontally, the link between the structures, and the role of the detachment horizons in the foreland part of the Zagros fold and thrust belt. The folding geometric parameters in each of the anticlines inside the cross-section have been precisely calculated. The NE Dezful Embayment district is marked by the significant activity of the faulting and the detachment horizons, which the thickness of the Gachsaran detachment horizon reaches 5 km after deformation. The thickness of this formation decreases along the SW Dezful Embayment district towards the southwest, and when it enters the Abadan Plain district and loses the salty units, its plastic behaviour declines and it loses its role in controlling the structural style. The fault activity and the detachment horizons decrease toward the southwest, reducing the structural complexity. Anticlines change from open fold to gentle fold based on the interlimb angle. The anticlines in the NE and SW Dezful Embayment districts are associated to the thrust faults and the detachment horizons, but but the anticlines in the Abadan Plain are classified as growth folds, characterized by the absence of significant detachment levels. The shortening observed in the Mishan Formation within this cross-section is 6.5 %. there is harmony in the number of the anticlines and the synclines above and below the Gachsaran detachment horizon.

    Stratigraphic structure and fault interpretation of the foreland basin system in the middle Taiwan Strait

    Su, Yung-HsiangWang, Tan K.Wege, Sebastian
    1.1-1.17页
    查看更多>>摘要:Since 2017, we have conducted several surveys to collect multi-channel seismic (MCS) and ocean-bottom seismometer (OBS) data in the middle Taiwan Strait. From the MCS data analysis, the fault distribution in the middle Taiwan Strait is mainly characterized by the normal faults. However, west of the Changyun Ridge, the fault distribution based on depth migrated sections is dominated by the strike-slip faults characterized by flower structures. The strike-slip faults were initiated between two rifted basins and reactivated after rifting. Based on the focal mechanisms and the striking direction of the faults, the strike-slip faults west of the Changyun Ridge are recognized to be left lateral. Additionally, several east-west trending left-lateral strike-slip faults were found in the middle Taiwan Strait. Based on the MCS data, we found that the changing direction of the strike-slip faults occurred in the middle Taiwan Strait before the formation of Taiwan, and was directly subject to the westward compression from the Philippine Sea Plate and the relative plate motion of the South China Sea with respect to the Philippine Sea Plate. Several 2.5 km-deep P-wave velocity models in the middle Taiwan Strait were imaged through inversion of refracted and reflected arrivals picked from the OBS data. At the boundary between the forebulge and foredeep, as well as within the sediment layers beneath the BU, a significant velocity gradient of approximately 2 s-1 was observed in both the lateral and vertical directions. Additionally, a fault-induced offset of about 0.2 km was identified in the sedimentary interfaces.

    Origin of the Late Jurassic Juyuan tungsten deposit in Central Jiangxi, South China: Constraints from in-situ U-Pb dating of wolframite, trace elements of tungsten minerals and Sr isotope of scheelite

    Zhang, JiLi, GuanglaiLi, ChengxiangWei, Xinglin...
    1.1-1.15页
    查看更多>>摘要:The Juyuan tungsten deposit is one of the few large quartz vein-type scheelite deposits in South China, but its ore-forming age and fluid evolution history remain unclear. In this study, we conducted U-Pb dating and trace element analysis of wolframite, as well as trace element and Sr isotope analysis of scheelite using in-situ LA-ICPMS and LA-MC-ICP-MS, respectively. The ore-forming age of the Juyuan tungsten deposit is 155.8 +/- 4.6 Ma (MSWD = 1.9), which is consistent with the magmatic age of the Juyuan granite porphyry. Wolframite exhibits a low delta Eu value and is enriched in Nb and Ta. The formation of Juyuan scheelite occurred in three stages: Sch-I scheelite has a high total REE content, a 'hump-shaped' chondrite-normalized REE distribution curve, and the lowest delta Eu value; Sch-II scheelite also has a high REE content, but the MREE gradually depletes, the chondritenormalized REE distribution curve flattens, and the delta Eu value increases; Sch-III scheelite shows significant MREE depletion, a concave distribution curve, and a strong positive Eu anomaly. The ore-forming environment was reduced in the early stage of Juyuan tungsten mineralization, but the introduction of atmospheric precipitation increased oxygen fugacity and decreased salinity. Sr isotope analysis of scheelite confirms that the Juyuan tungsten deposit is genetically related to the granite porphyry, and due to water-rock interactions, the initial 87Sr/86Sr ratio increased.