Pub Date : 2024-10-02DOI: 10.1016/j.jseaes.2024.106354
Xiaobo He, Qin Zhou
The Ryukyu subduction zone is typical of the subduction of an oceanic ridge (seamount or plateau) and back-arc rifting. How the upper plate responds to the combined effect of subduction of a bathymetric high and back-arc spreading is not fully understood. We investigate the combined effect by calculating the T-axis from regional focal mechanisms. Three patterns are observed from the outer rise to the back arc, showing a coherent trench-normal T-axis along the strike. They can be readily explained by outer-rise plate bending, forearc upper-plate bending induced by seamount subduction, and back-arc spreading associated with slab rollback. A distinct pattern of trench-parallel T-axes along the strike is also observed in the arc. This can be attributed to the difference in the extension rate between forearc extension and back-arc rifting of the upper plate, where the rate of back-arc extension driven by slab rollback is faster than that of forearc trench-normal extension attributed to seamount subduction. We also examine the T-axis patterns in other systems with seamount subduction, including the southern Manila subduction zone and the southern Central to northern South American subduction zones, displaying similar trench-normal T-axes in the forearc. Therefore, our observations have a broader implication in upper-plate deformation in response to seamount subduction.
琉球俯冲带是典型的洋脊（海山或高原）俯冲和弧后断裂现象。上层板块如何应对水深高地俯冲和弧后扩张的综合效应，目前尚不完全清楚。我们通过计算区域焦点机制的 T 轴来研究这种综合效应。从外隆起到背弧，我们观察到三种模式，沿走向显示出一致的海沟法向 T 轴。它们可以很容易地解释为外隆板块弯曲、海山俯冲引起的前弧上板块弯曲以及与板块回滚相关的后弧扩张。在弧内还观察到沿走向的沟槽平行 T 轴的明显模式。这可归因于上部板块的前弧延伸和后弧断裂在延伸速度上的差异，其中板块回滚驱动的后弧延伸速度快于海山俯冲导致的前弧海沟正常延伸速度。我们还研究了其他海山俯冲系统的 T 轴模式，包括马尼拉南部俯冲带和中美洲南部至南美洲北部俯冲带，它们在前弧都显示出类似的海沟正常 T 轴。因此，我们的观测结果对海山俯冲引起的上板块变形具有更广泛的意义。
{"title":"Explicit role of seamount subduction in upper plate deformation as exemplified in the Ryukyu subduction zone","authors":"Xiaobo He, Qin Zhou","doi":"10.1016/j.jseaes.2024.106354","DOIUrl":"10.1016/j.jseaes.2024.106354","url":null,"abstract":"<div><div>The Ryukyu subduction zone is typical of the subduction of an oceanic ridge (seamount or plateau) and back-arc rifting. How the upper plate responds to the combined effect of subduction of a bathymetric high and back-arc spreading is not fully understood. We investigate the combined effect by calculating the T-axis from regional focal mechanisms. Three patterns are observed from the outer rise to the back arc, showing a coherent trench-normal T-axis along the strike. They can be readily explained by outer-rise plate bending, forearc upper-plate bending induced by seamount subduction, and back-arc spreading associated with slab rollback. A distinct pattern of trench-parallel T-axes along the strike is also observed in the arc. This can be attributed to the difference in the extension rate between forearc extension and back-arc rifting of the upper plate, where the rate of back-arc extension driven by slab rollback is faster than that of forearc trench-normal extension attributed to seamount subduction. We also examine the T-axis patterns in other systems with seamount subduction, including the southern Manila subduction zone and the southern Central to northern South American subduction zones, displaying similar trench-normal T-axes in the forearc. Therefore, our observations have a broader implication in upper-plate deformation in response to seamount subduction.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"276 ","pages":"Article 106354"},"PeriodicalIF":2.7,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419347","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 : 2024-10-02DOI: 10.1016/j.jseaes.2024.106358
Tianqi Li , Yina Song , Ziyuan Chen , Lingling Xiao , Guodong Wang
The Kunyang phosphate deposit, located on the southwestern margin of the Yangtze Block in southern China, is hosted by the Lower Cambrian Meishucun Formation. The distribution of the deposit is restricted, and the outcrops of its phosphate layer are intermittent, probably owing to subsequent regional uplift and erosion. Therefore, investigating the denudation and uplift history of the deposit can clarify the preservation and distribution of the ore body after its formation, providing insights into the geological evolution of the mining area. Petrographic analysis indicates that collophane is the main ore mineral in the phosphorite, accompanied by dolomite, quartz, and limonite. The bulk-rock geochemical analyses suggest that the formation of phosphorite took place in a marine environment characterized by relative oxidation and high salinity, possibly involving hydrothermal activity during a drier mineralization stage. Apatite fission-track thermochronology, zircon-apatite (U-Th)/He dating, and thermal history modeling demonstrate that the Kunyang phosphate deposit underwent rapid uplift process during the Late Triassic (c. 225–211 Ma) and Eocene (c. 55–30 Ma), respectively. The average cooling rates were 1.05 °C/Myr and 0.93 °C/Myr, respectively, corresponding to average denudation rates of 42 m/Ma and 37 m/Ma. These two episodes of rapid uplift are corresponding to tectonic events on the southwestern margin of the Yangtze Plate during the Indosinian Orogeny, and the collision between the Eurasian and Indian Plates during the Himalayan Orogeny.
{"title":"Geochemistry and low-temperature thermochronology of Kunyang phosphate deposit in the Yangtze block and its regional uplift history","authors":"Tianqi Li , Yina Song , Ziyuan Chen , Lingling Xiao , Guodong Wang","doi":"10.1016/j.jseaes.2024.106358","DOIUrl":"10.1016/j.jseaes.2024.106358","url":null,"abstract":"<div><div>The Kunyang phosphate deposit, located on the southwestern margin of the Yangtze Block in southern China, is hosted by the Lower Cambrian Meishucun Formation. The distribution of the deposit is restricted, and the outcrops of its phosphate layer are intermittent, probably owing to subsequent regional uplift and erosion. Therefore, investigating the denudation and uplift history of the deposit can clarify the preservation and distribution of the ore body after its formation, providing insights into the geological evolution of the mining area. Petrographic analysis indicates that collophane is the main ore mineral in the phosphorite, accompanied by dolomite, quartz, and limonite. The bulk-rock geochemical analyses suggest that the formation of phosphorite took place in a marine environment characterized by relative oxidation and high salinity, possibly involving hydrothermal activity during a drier mineralization stage. Apatite fission-track thermochronology, zircon-apatite (U-Th)/He dating, and thermal history modeling demonstrate that the Kunyang phosphate deposit underwent rapid uplift process during the Late Triassic (c. 225–211 Ma) and Eocene (c. 55–30 Ma), respectively. The average cooling rates were 1.05 °C/Myr and 0.93 °C/Myr, respectively, corresponding to average denudation rates of 42 m/Ma and 37 m/Ma. These two episodes of rapid uplift are corresponding to tectonic events on the southwestern margin of the Yangtze Plate during the Indosinian Orogeny, and the collision between the Eurasian and Indian Plates during the Himalayan Orogeny.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"276 ","pages":"Article 106358"},"PeriodicalIF":2.7,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419349","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 : 2024-10-01DOI: 10.1016/j.jseaes.2024.106344
Xueyun Lu , Lining Wang , Jianqing Ji , Zhuxin Chen
In most analogue and numerical modelling studies for investigating the evolutionary mechanisms of fold-and-thrust belts, the initial models are typically designed as “sandboxes” with one side fixed in the horizontal direction. However, such model setup has neglected the potential effects of drainage divide migration. To address this issue, in this study we developed a 2D doubly vergent numerical model that accounts for drainage divide migration to investigate the structural evolution in Tianshan fold-and-thrust belts since the late Cenozoic, with an emphasis on the influences of climatic forcing on rock deformation. The deformation styles of northern and southern Tianshan fold-and-thrust belts exhibit significant differences, with the northern Tianshan fold-and-thrust belt characterized by deep isoclinal anticlines, whereas the southern Tianshan fold-and-thrust belts are dominated by thrust faults and minor shallow-level tight anticlines. Our modelling results suggest that such differences in deformation style may be attributed to the north–south precipitation gradient across Tianshan mountain. The results also show that unilateral climatic perturbations can lead to migration of the drainage divides towards the side with lower precipitation, thereby impacting the structural evolution on the opposite side of the mountain range. Such impact mainly manifests as an increased tendency to develop more thrust faults in the direction toward which the drainage divide is shifting. This provides a new perspective for reevaluating the patterns of tectonic evolution in the global orogenic belts since the late Cenozoic.
{"title":"Investigating the influence of climate on the evolution of fold-and-thrust belts in Chinese Tianshan: A 2D doubly vergent numerical model approach","authors":"Xueyun Lu , Lining Wang , Jianqing Ji , Zhuxin Chen","doi":"10.1016/j.jseaes.2024.106344","DOIUrl":"10.1016/j.jseaes.2024.106344","url":null,"abstract":"<div><div>In most analogue and numerical modelling studies for investigating the evolutionary mechanisms of fold-and-thrust belts, the initial models are typically designed as “sandboxes” with one side fixed in the horizontal direction. However, such model setup has neglected the potential effects of drainage divide migration. To address this issue, in this study we developed a 2D doubly vergent numerical model that accounts for drainage divide migration to investigate the structural evolution in Tianshan fold-and-thrust belts since the late Cenozoic, with an emphasis on the influences of climatic forcing on rock deformation. The deformation styles of northern and southern Tianshan fold-and-thrust belts exhibit significant differences, with the northern Tianshan fold-and-thrust belt characterized by deep isoclinal anticlines, whereas the southern Tianshan fold-and-thrust belts are dominated by thrust faults and minor shallow-level tight anticlines. Our modelling results suggest that such differences in deformation style may be attributed to the north–south precipitation gradient across Tianshan mountain. The results also show that unilateral climatic perturbations can lead to migration of the drainage divides towards the side with lower precipitation, thereby impacting the structural evolution on the opposite side of the mountain range. Such impact mainly manifests as an increased tendency to develop more thrust faults in the direction toward which the drainage divide is shifting. This provides a new perspective for reevaluating the patterns of tectonic evolution in the global orogenic belts since the late Cenozoic.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"276 ","pages":"Article 106344"},"PeriodicalIF":2.7,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419384","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 : 2024-10-01DOI: 10.1016/j.jseaes.2024.106345
Chao Han , Qiang Li , Haowei Jiang , QingQiang Meng , Xiao Gao , Ahmer Bilal , Shourui Dai , Xiaolin Du , Zhaopeng Wang , Zuozhen Han
Clarifying the mechanism of dolomitization is of pivotal importance and represents a burning issue among geologists. A comprehensive model to define the genesis of dolomitization in the Cambrian Chaomidian Formation carbonates is still lacking. In the highly focused study, the advanced integration of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), clumped isotope and carbon/oxygen isotope analyses was used to reveal complex interactions between the genesis and dolomitization of a stromatolite mound in the late Cambrian Chaomidian Formation of China. The results show that the dolomite content increases from bottom to top, along with a shift in lithology from limestone to dolostone. Additionally, as we moved from the base to the summit of the stromatolite mound, the Fe, Mn, and Na contents increase with increasing Mg levels, whereas the δ13C and δ18O values became more positive. Conversely, the levels of Sr and total rare earth elements (REEs) gradually decreased. The dolomite grains in the stromatolite mound are micritic and euhedral to subhedral, with foggy cores and bright edges and low cation ordering. The stromatolite limestone, dolostone, and underlying lime mudstone samples exhibit similar REE patterns: light REE enrichment, heavy REE loss, negative δEu anomalies, and weak negative δCe anomalies. The δ13C and δ18O values fall within the late Cambrian seawater range, suggesting that dolomitizing fluids originated mainly from concentrated seawater and migrated from top to bottom. The δ18O values indicate lower dolomite formation temperatures than calcite formation temperatures, supporting dolomitization during the penecontemporaneous diagenetic stage. Petrographic evidence reveals the presence of pyrite, indicating sulfate-reducing bacterial activity during diagenesis. XPS analysis revealed similar organic functional groups in both the stromatolite limestone and the dolostone, including C-(C = O)-O, C–C/C-(C–H), C-O and C-N. However, the dolostone spectrum exhibited a larger C-OH/C-O peak area, suggesting significant microbial organic matter involvement in dolomite formation. While a kinetic obstacle is recognized as a primary cause of dolomite formation, this study also suggested that microbial activity weakened this obstacle during diagenesis. Thus, microbial metabolism or cyanobacterial decomposition facilitates dolomite formation during the penecontemporaneous diagenetic stage.
{"title":"The mechanism of dolomitization in a stromatolite mound in the late Cambrian Chaomidian Formation, Shandong Province, China","authors":"Chao Han , Qiang Li , Haowei Jiang , QingQiang Meng , Xiao Gao , Ahmer Bilal , Shourui Dai , Xiaolin Du , Zhaopeng Wang , Zuozhen Han","doi":"10.1016/j.jseaes.2024.106345","DOIUrl":"10.1016/j.jseaes.2024.106345","url":null,"abstract":"<div><div>Clarifying the mechanism of dolomitization is of pivotal importance and represents a burning issue among geologists. A comprehensive model to define the genesis of dolomitization in the Cambrian Chaomidian Formation carbonates is still lacking. In the highly focused study, the advanced integration of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), clumped isotope and carbon/oxygen isotope analyses was used to reveal complex interactions between the genesis and dolomitization of a stromatolite mound in the late Cambrian Chaomidian Formation of China. The results show that the dolomite content increases from bottom to top, along with a shift in lithology from limestone to dolostone. Additionally, as we moved from the base to the summit of the stromatolite mound, the Fe, Mn, and Na contents increase with increasing Mg levels, whereas the δ<sup>13</sup>C and δ<sup>18</sup>O values became more positive. Conversely, the levels of Sr and total rare earth elements (REEs) gradually decreased. The dolomite grains in the stromatolite mound are micritic and euhedral to subhedral, with foggy cores and bright edges and low cation ordering. The stromatolite limestone, dolostone, and underlying lime mudstone samples exhibit similar REE patterns: light REE enrichment, heavy REE loss, negative δEu anomalies, and weak negative δCe anomalies. The δ<sup>13</sup>C and δ<sup>18</sup>O values fall within the late Cambrian seawater range, suggesting that dolomitizing fluids originated mainly from concentrated seawater and migrated from top to bottom. The δ<sup>18</sup>O values indicate lower dolomite formation temperatures than calcite formation temperatures, supporting dolomitization during the penecontemporaneous diagenetic stage. Petrographic evidence reveals the presence of pyrite, indicating sulfate-reducing bacterial activity during diagenesis. XPS analysis revealed similar organic functional groups in both the stromatolite limestone and the dolostone, including C-(C = O)-O, C–C/C-(C–H), C-O and C-N. However, the dolostone spectrum exhibited a larger C-OH/C-O peak area, suggesting significant microbial organic matter involvement in dolomite formation. While a kinetic obstacle is recognized as a primary cause of dolomite formation, this study also suggested that microbial activity weakened this obstacle during diagenesis. Thus, microbial metabolism or cyanobacterial decomposition facilitates dolomite formation during the penecontemporaneous diagenetic stage.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"276 ","pages":"Article 106345"},"PeriodicalIF":2.7,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142437711","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}
Palaeoflood events represent immediate hydrological responses to extreme climate change. A loess-paleosol sedimentary profile containing three overbank flood deposits (OFD1, OFD2, and OFD3) layers that recorded palaeoflood events was discovered on the platform scarp of the Shahe River, a tributary of the Huaihe River through a field investigation. Sediment samples were collected, and their physicochemical properties, as well as optically stimulated luminescence (OSL) dating, were analyzed. The results indicated that OFD1, OFD2, and OFD3 were indeed overbank flood deposits influenced by hydrodynamic forces. However, OFD3 and OFD1 consisted primarily of sand (>60 %) in terms of particle size composition, whereas paleosol (S0), transitional loess (Lt), and Malan loess (L1) mainly comprised silt (>70 %). Moreover, the magnetic susceptibility values of OFD3 and OFD1 exceeded those of S0, Lt, and L1. The contents of Na2O, K2O, and SiO2 were higher, while their contents of Al2O3 and Fe2O3 were lower in OFD3 and OFD1. These suggested that OFD3 and OFD1 may originate from weathered bedrock materials transported from the upper reaches of the Shahe River under significant hydrodynamic forces. The particle size composition, magnetic susceptibility value, and geochemical element composition of OFD2 were similar to those of S0, Lt, and L1 but diverged significantly from those of OFD1 and OFD3, indicating that OFD2 originated from loess and soil sediments widely distributed on both sides of the valley. Through OSL dating and stratigraphic chronological framework of the sedimentary profile, these three extraordinary palaeoflood events in the Huaihe River Basin occurred during the late Holocene, ∼1470 a. The analysis of high-resolution climate proxy indicators, atmospheric circulation factors, and global mean temperature demonstrated a direct correlation between these extreme flood events and abrupt climate changes during ∼ 1470 a. This period corresponded to severe climate deterioration during the Northern and Southern Dynasties (589–420 CE) in China. These findings are crucial for enhancing our understanding of regional hydrological climate responses to global changes.
{"title":"Late Holocene extraordinary palaeoflood events and their climatological context in the Shahe River, Huaihe River Basin, China","authors":"Lijun Shang , Xiaochun Zha, Chunchang Huang, Yuqin Li, Jiangli Pang, Yali Zhou, Yang Liu, Yuwei Wen","doi":"10.1016/j.jseaes.2024.106346","DOIUrl":"10.1016/j.jseaes.2024.106346","url":null,"abstract":"<div><div>Palaeoflood events represent immediate hydrological responses to extreme climate change. A loess-paleosol sedimentary profile containing three overbank flood deposits (OFD1, OFD2, and OFD3) layers that recorded palaeoflood events was discovered on the platform scarp of the Shahe River, a tributary of the Huaihe River through a field investigation. Sediment samples were collected, and their physicochemical properties, as well as optically stimulated luminescence (OSL) dating, were analyzed. The results indicated that OFD1, OFD2, and OFD3 were indeed overbank flood deposits influenced by hydrodynamic forces. However, OFD3 and OFD1 consisted primarily of sand (>60 %) in terms of particle size composition, whereas paleosol (S<sub>0</sub>), transitional loess (L<sub>t</sub>), and Malan loess (L<sub>1</sub>) mainly comprised silt (>70 %). Moreover, the magnetic susceptibility values of OFD3 and OFD1 exceeded those of S<sub>0</sub>, L<sub>t</sub>, and L<sub>1</sub>. The contents of Na<sub>2</sub>O, K<sub>2</sub>O, and SiO<sub>2</sub> were higher, while their contents of Al<sub>2</sub>O<sub>3</sub> and Fe<sub>2</sub>O<sub>3</sub> were lower in OFD3 and OFD1. These suggested that OFD3 and OFD1 may originate from weathered bedrock materials transported from the upper reaches of the Shahe River under significant hydrodynamic forces. The particle size composition, magnetic susceptibility value, and geochemical element composition of OFD2 were similar to those of S<sub>0</sub>, L<sub>t</sub>, and L<sub>1</sub> but diverged significantly from those of OFD1 and OFD3, indicating that OFD2 originated from loess and soil sediments widely distributed on both sides of the valley. Through OSL dating and stratigraphic chronological framework of the sedimentary profile, these three extraordinary palaeoflood events in the Huaihe River Basin occurred during the late Holocene, ∼1470 a. The analysis of high-resolution climate proxy indicators, atmospheric circulation factors, and global mean temperature demonstrated a direct correlation between these extreme flood events and abrupt climate changes during ∼ 1470 a. This period corresponded to severe climate deterioration during the Northern and Southern Dynasties (589–420 CE) in China. These findings are crucial for enhancing our understanding of regional hydrological climate responses to global changes.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"276 ","pages":"Article 106346"},"PeriodicalIF":2.7,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419350","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 : 2024-10-01DOI: 10.1016/j.jseaes.2024.106353
Jianfeng Liu , Jinyi Li , Shuo Zhao , Junfeng Qu , Maohui Ge , Qianlu Lv
As the largest Phanerozoic accretionary orogenic belt, whether the Central Asian Orogenic Belt (CAOB) experienced a strong collisional orogenic process after Paleo-Asian Ocean (PAO) closure remains controversial. The age and P-T conditions recorded by metamorphic rocks could be used to study the thermal and tectonic regimes during orogenic processes, providing constraints for orogenic evolution. In this paper, the geochronology and metamorphism of a newly discovered metamorphic ophiolite mélange in the Banlashan area near the Xar Moron River in the southeastern CAOB were studied. The association and age of the metamorphic ophiolite mélange protoliths are similar to those of the Xar Moron River ophiolite belt to the north. The metamorphic ages of different ophiolite mélange lithologies are all late Permian (250.2–256.5 Ma), indicating that the Siberian and Sino-Korean paleoplates collided during the late Permian. The metamorphic pressure and temperature recorded by the garnet amphibolite block in the ophiolite mélange could reach 8.5–8.8 kbar and 700–725 ℃. The core-to-rim zoning of garnet indicates that the garnet amphibolite underwent a clockwise P–T path, which is the typical metamorphic feature of collisional orogens. The ophiolite mélange metamorphic features, combined with regional magmatic, metamorphic, sedimentary and tectonic deformation data, indicate that a strong collisional orogeny occurred rather than a soft orogeny between the Siberian and Sino-Korean paleoplates after the PAO closure.
作为新生代最大的增生造山带，中亚造山带在古亚洲洋关闭后是否经历了强烈的碰撞造山过程仍存在争议。变质岩记录的年龄和P-T条件可用于研究造山过程中的热机制和构造机制，为造山演化提供约束。本文研究了中国大洋洲东部Xar Moron河附近Banlashan地区新发现的变质蛇绿岩混合体的地质年代和变质作用。变质蛇绿混杂岩原岩的关联和年龄与北面的Xar Moron河蛇绿混杂岩带相似。不同蛇绿岩混合岩性的变质年龄均为二叠纪晚期（250.2-256.5Ma），表明西伯利亚古地层与中韩古地层在二叠纪晚期发生碰撞。蛇绿混杂岩中的石榴石闪长岩块记录的变质压力和温度可达 8.5-8.8 千巴和 700-725 ℃。石榴石从岩芯到边缘的分带表明，石榴石闪长岩经历了顺时针的P-T路径，这是碰撞造山运动的典型变质特征。蛇绿混杂岩的变质特征，结合区域岩浆、变质、沉积和构造变形数据，表明 PAO 闭合后，西伯利亚古陆和中韩古陆之间发生了强碰撞造山作用，而不是软造山作用。
{"title":"Collisional orogeny between the Siberian and Sino-Korean paleoplates: Evidence from geochronology and metamorphism of the metamorphic ophiolite mélange in the Banlashan area near the Xar Moron River in the southeastern Central Asian orogenic belt","authors":"Jianfeng Liu , Jinyi Li , Shuo Zhao , Junfeng Qu , Maohui Ge , Qianlu Lv","doi":"10.1016/j.jseaes.2024.106353","DOIUrl":"10.1016/j.jseaes.2024.106353","url":null,"abstract":"<div><div>As the largest Phanerozoic accretionary orogenic belt, whether the Central Asian Orogenic Belt (CAOB) experienced a strong collisional orogenic process after Paleo-Asian Ocean (PAO) closure remains controversial. The age and P-T conditions recorded by metamorphic rocks could be used to study the thermal and tectonic regimes during orogenic processes, providing constraints for orogenic evolution. In this paper, the geochronology and metamorphism of a newly discovered metamorphic ophiolite mélange in the Banlashan area near the Xar Moron River in the southeastern CAOB were studied. The association and age of the metamorphic ophiolite mélange protoliths are similar to those of the Xar Moron River ophiolite belt to the north. The metamorphic ages of different ophiolite mélange lithologies are all late Permian (250.2–256.5 Ma), indicating that the Siberian and Sino-Korean paleoplates collided during the late Permian. The metamorphic pressure and temperature recorded by the garnet amphibolite block in the ophiolite mélange could reach 8.5–8.8 kbar and 700–725 ℃. The core-to-rim zoning of garnet indicates that the garnet amphibolite underwent a clockwise P–T path, which is the typical metamorphic feature of collisional orogens. The ophiolite mélange metamorphic features, combined with regional magmatic, metamorphic, sedimentary and tectonic deformation data, indicate that a strong collisional orogeny occurred rather than a soft orogeny between the Siberian and Sino-Korean paleoplates after the PAO closure.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"276 ","pages":"Article 106353"},"PeriodicalIF":2.7,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419346","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 : 2024-09-30DOI: 10.1016/j.jseaes.2024.106341
Mingdong Zhang , Shucheng Tan , Mengfei Ruan , Liang Li , Qinghe Yan
The Triassic granitoids in the East Kunlun Orogenic Belt (EKOB) are crucial for understanding the tectonic evolution of the Paleo-Tethys Ocean. This study presents zircon U–Pb ages, Lu–Hf isotopes, whole-rock major and trace elements, and Sr–Nd isotope compositions from monzogranite plutons in the central segment of EKOB to constrain their petrogenesis and tectonic evolution. These monzogranites are dominant composed of mineral assemblages of K-feldspars, plagioclase, minor biotite and accessory minerals. U–Pb dating of zircons from the Xinle South (XLS), Nanshankou (NSK) and Changgou South (CGS) plutons yield ages of 251 Ma, 232 Ma and 221 Ma, respectively. The studied monzogranites have relatively high SiO2 and Al2O3, but have low contents of TiO2, Fe2O3T, MgO relative to the coeval granodiorites. These monzogranites are classified as fractionated I-type granites, ranging from calc-alkaline to high-K calc-alkaline compositions. Their negative εNd(t) values (−4.2 to −6.3) and zircon εHf(t) values (−6.1 to −9.3) suggest that magma generation occurred through partial melting of ancient lower crust, followed by extensive fractional crystallization. Integrating our new data with regional geological evidence, we propose that the Early Triassic XLS monzogranite emplaced in a localized extensional environment linked to the northward subduction of the Paleo-Tethys oceanic plate. In contrast, during the post-collisional extensional phase of the Late Triassic, the formation of the NSK and CGS monzogranite plutons was directly influenced by asthenospheric upwelling, lower crust delamination, and subsequent continental rifting.
东昆仑造山带（EKOB）的三叠纪花岗岩对于了解古特提斯洋的构造演化至关重要。本研究介绍了东昆仑造山带中段单斜花岗岩柱岩的锆石U-Pb年龄、Lu-Hf同位素、全岩主要元素和痕量元素以及Sr-Nd同位素组成，以对其成岩和构造演化进行约束。这些单斜花岗岩主要由 K 长石、斜长石、少量斜长石和附属矿物组成。对新乐南（XLS）、南山口（NSK）和长沟南（CGS）岩柱的锆石进行 U-Pb 测定，得出的年龄分别为 251 Ma、232 Ma 和 221 Ma。与共生花岗闪长岩相比，所研究的单斜花岗岩的SiO2和Al2O3含量相对较高，但TiO2、Fe2O3T和MgO含量较低。这些单斜花岗岩被归类为分馏I型花岗岩，成分从钙碱性到高K钙碱性不等。它们的负εNd(t)值（-4.2至-6.3）和锆石εHf(t)值（-6.1至-9.3）表明，岩浆的生成是通过古代下地壳的部分熔化，然后进行广泛的分馏结晶。综合我们的新数据和区域地质证据，我们认为早三叠世XLS单斜岩是在与古特提斯大洋板块向北俯冲有关的局部延伸环境中形成的。与此相反，在晚三叠世的碰撞后伸展阶段，NSK和CGS单斜岩体的形成直接受到了星体层上涌、下地壳分层以及随后的大陆裂动的影响。
{"title":"Petrogenesis and tectonic implication of the Triassic monzogranite from the central segment of the East Kunlun Orogen, NW China","authors":"Mingdong Zhang , Shucheng Tan , Mengfei Ruan , Liang Li , Qinghe Yan","doi":"10.1016/j.jseaes.2024.106341","DOIUrl":"10.1016/j.jseaes.2024.106341","url":null,"abstract":"<div><div>The Triassic granitoids in the East Kunlun Orogenic Belt (EKOB) are crucial for understanding the tectonic evolution of the Paleo-Tethys Ocean. This study presents zircon U–Pb ages, Lu–Hf isotopes, whole-rock major and trace elements, and Sr–Nd isotope compositions from monzogranite plutons in the central segment of EKOB to constrain their petrogenesis and tectonic evolution. These monzogranites are dominant composed of mineral assemblages of K-feldspars, plagioclase, minor biotite and accessory minerals. U–Pb dating of zircons from the Xinle South (XLS), Nanshankou (NSK) and Changgou South (CGS) plutons yield ages of 251 Ma, 232 Ma and 221 Ma, respectively. The studied monzogranites have relatively high SiO<sub>2</sub> and Al<sub>2</sub>O<sub>3</sub>, but have low contents of TiO<sub>2</sub>, Fe<sub>2</sub>O<sub>3</sub><sup>T</sup>, MgO relative to the coeval granodiorites. These monzogranites are classified as fractionated I-type granites, ranging from calc-alkaline to high-K calc-alkaline compositions. Their negative εNd(t) values (−4.2 to −6.3) and zircon εHf(t) values (−6.1 to −9.3) suggest that magma generation occurred through partial melting of ancient lower crust, followed by extensive fractional crystallization. Integrating our new data with regional geological evidence, we propose that the Early Triassic XLS monzogranite emplaced in a localized extensional environment linked to the northward subduction of the Paleo-Tethys oceanic plate. In contrast, during the post-collisional extensional phase of the Late Triassic, the formation of the NSK and CGS monzogranite plutons was directly influenced by asthenospheric upwelling, lower crust delamination, and subsequent continental rifting.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"276 ","pages":"Article 106341"},"PeriodicalIF":2.7,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419385","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 : 2024-09-30DOI: 10.1016/j.jseaes.2024.106340
Di Shen , Ming Wang , Chang-sheng Yu , Quewang Danzeng , Sheng-shuo Zhang , Jin-lu Zhou , Bin-xuan Hao
Post-collisional mafic rocks provide valuable insights into the mantle properties and evolution of orogenic belts. However, their origins remain unknown. In this study, comprehensive age, elemental, and zircon Lu–Hf isotopic data are presented for mafic dikes from the Asuo area of the Central Tibetan Plateau. The Asuo mafic dikes exhibit typical arc-related characteristics such as enrichment in large-ion lithophile elements and depletion in high-field-strength elements. This sodium-rich calc-alkaline mafic rocks has low K2O contents (0.98–1.26 wt%) and high Na2O/K2O ratios (2.55–2.97). The presence of xenolith zircons and varying zircon Hf isotopic composition [εHf(t): 1.33–8.32] indicate that the mafic magma assimilated juvenile crust. Zircon U-Pb dating results suggest that the Asuo mafic rocks were emplaced contemporaneously with the adakite-like rocks during ∼ 95–75 Ma. However, no genetic link between Asuo mafic rocks and the adakite-like rocks in the Lhasa–Qiangtang Orogenic belt was observed. The primary contribution of mantle-derived mafic magmas to the formation of coeval intermediate–felsic magmas is the provision of additional heat. The mass exchange between them may be limited. We suggest a geodynamic scenario in which the orogenic root may have been removed during the post-collisional period via repeated and localized lithospheric dripping. In this model, the formation of mafic and adakite-like intrusions occurred in two stages, that is, (1) partial melting of metasomatized lithospheric mantle generated mafic melts, and (2) underplating of these mafic melts beneath the thickened juvenile lower crust, which resulted in partial melting of the juvenile mafic lower crust and generation of adakite-like melts. Our results provide new insights into the magmatism in the terminal stage of an orogenic system.
{"title":"Discovery of Late Cretaceous basalts in the Asuo area, Central Tibet: Implications for orogenic root removal beneath the Lhasa-Qiangtang orogenic belt","authors":"Di Shen , Ming Wang , Chang-sheng Yu , Quewang Danzeng , Sheng-shuo Zhang , Jin-lu Zhou , Bin-xuan Hao","doi":"10.1016/j.jseaes.2024.106340","DOIUrl":"10.1016/j.jseaes.2024.106340","url":null,"abstract":"<div><div>Post-collisional mafic rocks provide valuable insights into the mantle properties and evolution of orogenic belts. However, their origins remain unknown. In this study, comprehensive age, elemental, and zircon Lu–Hf isotopic data are presented for mafic dikes from the Asuo area of the Central Tibetan Plateau. The Asuo mafic dikes exhibit typical arc-related characteristics such as enrichment in large-ion lithophile elements and depletion in high-field-strength elements. This sodium-rich calc-alkaline mafic rocks has low K<sub>2</sub>O contents (0.98–1.26 wt%) and high Na<sub>2</sub>O/K<sub>2</sub>O ratios (2.55–2.97). The presence of xenolith zircons and varying zircon Hf isotopic composition [ε<sub>Hf</sub>(t): 1.33–8.32] indicate that the mafic magma assimilated juvenile crust. Zircon U-Pb dating results suggest that the Asuo mafic rocks were emplaced contemporaneously with the adakite-like rocks during ∼ 95–75 Ma. However, no genetic link between Asuo mafic rocks and the adakite-like rocks in the Lhasa–Qiangtang Orogenic belt was observed. The primary contribution of mantle-derived mafic magmas to the formation of coeval intermediate–felsic magmas is the provision of additional heat. The mass exchange between them may be limited. We suggest a geodynamic scenario in which the orogenic root may have been removed during the post-collisional period via repeated and localized lithospheric dripping. In this model, the formation of mafic and adakite-like intrusions occurred in two stages, that is, (1) partial melting of metasomatized lithospheric mantle generated mafic melts, and (2) underplating of these mafic melts beneath the thickened juvenile lower crust, which resulted in partial melting of the juvenile mafic lower crust and generation of adakite-like melts. Our results provide new insights into the magmatism in the terminal stage of an orogenic system.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"276 ","pages":"Article 106340"},"PeriodicalIF":2.7,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419386","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 : 2024-09-30DOI: 10.1016/j.jseaes.2024.106342
Varoujan K. Sissakian , Lanja H. Abdullah , Ala Ghafur
The Iraqi territory forms the northeastern part of the Arabian Plate, which is in collision with the Eurasian Plate. The collision of the plates has formed the Zagros Foreland Basin, which includes the Zagros Fold–Thrust Belt. The belt covers the majority of the northern part of Iraq (Kurdistan Region of Iraq) and parts of the central part of Iraq. South of the belt, the Mesopotamian Foredeep is developed. All these parts of Iraq are considered tectonically unstable. To the west and south of the Mesopotamian Foredeep, the tectonically stable part is developed that has been affected by a lesser amount of deformation as compared to the remaining unstable parts by the exerted forces related to the collision of both plates. All researchers have divided tectonically Iraq into two main tectonic domains; called Stable and Unstable shelves, which are further divided into zones and sub-zones. However, different terms and names were used by different researchers, which has confused readers and workers who have dealt with the tectonics of the Iraqi territory. We have reviewed and discussed all existing divisions by different researchers and have suggested new terminology using the existing maps, reports, scientific published articles, and interpreting satellite images, besides field observations. Moreover, we presented a tectonic map with the suggested new terminology.
{"title":"Tectonic framework of Iraq. A critical review and discussion","authors":"Varoujan K. Sissakian , Lanja H. Abdullah , Ala Ghafur","doi":"10.1016/j.jseaes.2024.106342","DOIUrl":"10.1016/j.jseaes.2024.106342","url":null,"abstract":"<div><div>The Iraqi territory forms the northeastern part of the Arabian Plate, which is in collision with the Eurasian Plate. The collision of the plates has formed the Zagros Foreland Basin, which includes the Zagros Fold–Thrust Belt. The belt covers the majority of the northern part of Iraq (Kurdistan Region of Iraq) and parts of the central part of Iraq. South of the belt, the Mesopotamian Foredeep is developed. All these parts of Iraq are considered tectonically unstable. To the west and south of the Mesopotamian Foredeep, the tectonically stable part is developed that has been affected by a lesser amount of deformation as compared to the remaining unstable parts by the exerted forces related to the collision of both plates. All researchers have divided tectonically Iraq into two main tectonic domains; called Stable and Unstable shelves, which are further divided into zones and sub-zones. However, different terms and names were used by different researchers, which has confused readers and workers who have dealt with the tectonics of the Iraqi territory. We have reviewed and discussed all existing divisions by different researchers and have suggested new terminology using the existing maps, reports, scientific published articles, and interpreting satellite images, besides field observations. Moreover, we presented a tectonic map with the suggested new terminology.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"276 ","pages":"Article 106342"},"PeriodicalIF":2.7,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142437710","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 : 2024-09-26DOI: 10.1016/j.jseaes.2024.106338
Jinze Wang , Hongyi Li , Yuting Zhang , Haipeng Li , Yanzhen Li , Zeyu Ma , Yifan Xiang
The Longmen Shan (LMS) fault zone located in the southwest of China is not only the boundary tectonic zone of the Tibetan Plateau and South China block, but also an important part of the north–south seismic belt of China. To investigate the detailed crustal structure of the LMS fault zone, we deployed a dense seismic array of 151 short-period temporary stations in its northern section from March 16 to April 6, 2023. Continuous vertical component ambient noise waveforms recorded by these stations were cross-correlated for all station pairs, enabling the extraction of Rayleigh wave phase velocity dispersion curves across periods ranging from 0.5 s to 6 s. We then inverted these data to derive the crustal shear wave velocity using direct surface wave tomography. Meanwhile, a linear sub-array consisting of 54 stations and crossing the surface rupture of the 2008 Wenchuan earthquake was used to image the fault structure by applying the Transmitted Surface Wave Reverse Time Migration method (TSW-RTM). The ambient noise tomography results show that strong lateral heterogeneity exists in the shallow crust in the study area, with a high shear velocity in the northwest and a low shear velocity in the southeast. The low shear velocity is generally distributed between the Yingxiu-Beichuan fault (YBF) and the Guanxian-Jiangyou fault (GJF). The results of TSW-RTM indicate that the Wenchuan-Maoxian fault (WMF) and the YBF are both characterized with a steep dip to the northwest. Our results could serve as the important basis for the study of segmentation characteristics of the LMS fault and seismic hazard preparation and mitigation.
{"title":"Shallow crustal structure of the northern Longmen Shan fault zone revealed by a dense seismic array with ambient noise analysis","authors":"Jinze Wang , Hongyi Li , Yuting Zhang , Haipeng Li , Yanzhen Li , Zeyu Ma , Yifan Xiang","doi":"10.1016/j.jseaes.2024.106338","DOIUrl":"10.1016/j.jseaes.2024.106338","url":null,"abstract":"<div><div>The Longmen Shan (LMS) fault zone located in the southwest of China is not only the boundary tectonic zone of the Tibetan Plateau and South China block, but also an important part of the north–south seismic belt of China. To investigate the detailed crustal structure of the LMS fault zone, we deployed a dense seismic array of 151 short-period temporary stations in its northern section from March 16 to April 6, 2023. Continuous vertical component ambient noise waveforms recorded by these stations were cross-correlated for all station pairs, enabling the extraction of Rayleigh wave phase velocity dispersion curves across periods ranging from 0.5 s to 6 s. We then inverted these data to derive the crustal shear wave velocity using direct surface wave tomography. Meanwhile, a linear sub-array consisting of 54 stations and crossing the surface rupture of the 2008 Wenchuan earthquake was used to image the fault structure by applying the Transmitted Surface Wave Reverse Time Migration method (TSW-RTM). The ambient noise tomography results show that strong lateral heterogeneity exists in the shallow crust in the study area, with a high shear velocity in the northwest and a low shear velocity in the southeast. The low shear velocity is generally distributed between the Yingxiu-Beichuan fault (YBF) and the Guanxian-Jiangyou fault (GJF). The results of TSW-RTM indicate that the Wenchuan-Maoxian fault (WMF) and the YBF are both characterized with a steep dip to the northwest. Our results could serve as the important basis for the study of segmentation characteristics of the LMS fault and seismic hazard preparation and mitigation.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"276 ","pages":"Article 106338"},"PeriodicalIF":2.7,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419344","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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