Abstract The tectonic evolution of the Paleo-Asian Ocean (PAO) has been well studied, including its gradual narrowing and closure by subduction. However, aspects of the tectonic evolution of the oceanic domain remain unclear, including the exact timing and nature of the closure. The Central Asian Orogenic Belt (CAOB) was formed by the closure of the PAO and, therefore, contains information about the tectonic evolution of the oceanic domain. Here, we report a study of the petrology, geochronology, and geochemistry of the Taohaiyingzi section of the Permian Linxi Formation in Alukhorqin Banner (Northeast China) in the central part of the CAOB. A newly discovered andesitic tuff from the lower part of the Linxi Formation yields a weighted mean 206Pb/238U age of 262.2 ± 1.1 Ma (n = 87), indicating that the lower part of the Linxi Formation of the Taohaiyingzi section was deposited during the late Guadalupian. Provenance weathering indicators show that the sedimentary rocks of the Linxi Formation are of low maturity. Element geochemical characteristics indicate that the Linxi Formation clastic rocks were derived from eroded magmatic rocks that formed in a continental arc setting and were deposited close to the arc in a continental arc basin environment. The active margin setting was generated by the subduction of the paleo-Asian oceanic plate beneath the Xilinhot–Songliao block. The inferred palaeosalinity of the sedimentary environment changed gradually from brackish to fresh water, suggesting the end of oceanic plate subduction during the late Guadalupian, and the closure of the PAO during or after the Lopingian.
摘要古亚洲洋(PAO)的构造演化已被广泛研究，包括其逐渐变窄和俯冲闭合。然而，大洋域的构造演化方面仍然不清楚，包括确切的时间和关闭的性质。中亚造山带(CAOB)是由中亚造山带的闭合而形成的，因此它包含了洋域构造演化的信息。本文对中国东北阿鲁科尔沁中部二叠系林西组桃海营子剖面进行了岩石学、年代学和地球化学研究。新发现的临西组下段安山岩凝灰岩的加权平均206Pb/238U年龄为262.2±1.1 Ma (n = 87)，表明桃海营子剖面临西组下段沉积于瓜达鲁普期晚期。物源风化指标表明，林西组沉积岩成熟度较低。元素地球化学特征表明，林西组碎屑岩来源于大陆弧环境下的侵蚀岩浆岩，并在大陆弧盆地环境下沉积于弧附近。活动边缘环境是由古亚洲大洋板块在锡林浩特—松辽地块下的俯冲作用形成的。推断沉积环境的古盐度由咸淡水逐渐变为淡水，表明瓜达鲁普期晚期洋板俯冲结束，洛平期或之后PAO闭合。
{"title":"Volcanic Age and Geochemistry of the Permian Linxi Formation in Northeast China: Implications for the Tectonic Evolution of the Paleo-Asian Ocean","authors":"Haihua Zhang, Hua Zhang, Shuzhong Shen, Zifu Zhao, Liang Qiu, Shuwang Chen, Jian Zhang, Fanhao Gong, Yongfei Li, Yuejuan Zheng, Shouliang Sun, Yujin Zhang","doi":"10.2113/2023/lithosphere_2023_192","DOIUrl":"https://doi.org/10.2113/2023/lithosphere_2023_192","url":null,"abstract":"Abstract The tectonic evolution of the Paleo-Asian Ocean (PAO) has been well studied, including its gradual narrowing and closure by subduction. However, aspects of the tectonic evolution of the oceanic domain remain unclear, including the exact timing and nature of the closure. The Central Asian Orogenic Belt (CAOB) was formed by the closure of the PAO and, therefore, contains information about the tectonic evolution of the oceanic domain. Here, we report a study of the petrology, geochronology, and geochemistry of the Taohaiyingzi section of the Permian Linxi Formation in Alukhorqin Banner (Northeast China) in the central part of the CAOB. A newly discovered andesitic tuff from the lower part of the Linxi Formation yields a weighted mean 206Pb/238U age of 262.2 ± 1.1 Ma (n = 87), indicating that the lower part of the Linxi Formation of the Taohaiyingzi section was deposited during the late Guadalupian. Provenance weathering indicators show that the sedimentary rocks of the Linxi Formation are of low maturity. Element geochemical characteristics indicate that the Linxi Formation clastic rocks were derived from eroded magmatic rocks that formed in a continental arc setting and were deposited close to the arc in a continental arc basin environment. The active margin setting was generated by the subduction of the paleo-Asian oceanic plate beneath the Xilinhot–Songliao block. The inferred palaeosalinity of the sedimentary environment changed gradually from brackish to fresh water, suggesting the end of oceanic plate subduction during the late Guadalupian, and the closure of the PAO during or after the Lopingian.","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135484765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Songyan Liu, Kangxing Shi, Da Zhang, Changming Wang, Bin Du, Qi Chen, Lei Gao
Abstract High-Mg adakite rocks preserve crucial information about the crust-mantle interactions during the magma evolution. The Luxi Terrane, southeastern North China Craton, stores a set of Early Cretaceous high-Mg adakite rocks; nevertheless, their petrogenesis remains controversial. In this study, we present new whole-rock geochemistry, zircon U-Pb-Hf isotopes in the Tiezhai, Jinxingtou, and Sanshanyu complexes which are composed of gabbroic diorite, diorites, syenites, and monzonites. Field observations and zircon U-Pb dating indicate that all of the rock units crystallized contemporaneously at ca. 125–120 Ma. They are characterized by high Al2O3 and Sr contents, and low MgO, Y, Yb, and heavy rare earth elements contents, coupled with high Sr/Y values (42–163), showing adakitic affinities. The magma mixing process is supported by the following ample evidence: (1) the disequilibrium mineral textures and mafic enclaves; (2) high Mg# values (37–69, Mean = 58); and (3) widely zircons εHf(t) values (−25.6 to +7.8). The signature geochemical characteristics support that the adakites were generated by magma mixing of ancient crust-derived melts and relatively mafic melts from metasomatized mantle source. In combined with regional geology, the Early Cretaceous high-Mg adakites in Luxi Terrane represent the magmatic response of intensive crust-mantle interaction caused by the underplating of voluminous mantle-derived magma in an extension intracontinental setting.
{"title":"Crust-Mantle Interaction Controls the Formation of High-Mg Adakitic Rocks: Evidence from Early Cretaceous Intrusive Complexes in Luxi Terrane, North China Craton","authors":"Songyan Liu, Kangxing Shi, Da Zhang, Changming Wang, Bin Du, Qi Chen, Lei Gao","doi":"10.2113/2023/8019744","DOIUrl":"https://doi.org/10.2113/2023/8019744","url":null,"abstract":"Abstract High-Mg adakite rocks preserve crucial information about the crust-mantle interactions during the magma evolution. The Luxi Terrane, southeastern North China Craton, stores a set of Early Cretaceous high-Mg adakite rocks; nevertheless, their petrogenesis remains controversial. In this study, we present new whole-rock geochemistry, zircon U-Pb-Hf isotopes in the Tiezhai, Jinxingtou, and Sanshanyu complexes which are composed of gabbroic diorite, diorites, syenites, and monzonites. Field observations and zircon U-Pb dating indicate that all of the rock units crystallized contemporaneously at ca. 125–120 Ma. They are characterized by high Al2O3 and Sr contents, and low MgO, Y, Yb, and heavy rare earth elements contents, coupled with high Sr/Y values (42–163), showing adakitic affinities. The magma mixing process is supported by the following ample evidence: (1) the disequilibrium mineral textures and mafic enclaves; (2) high Mg# values (37–69, Mean = 58); and (3) widely zircons εHf(t) values (−25.6 to +7.8). The signature geochemical characteristics support that the adakites were generated by magma mixing of ancient crust-derived melts and relatively mafic melts from metasomatized mantle source. In combined with regional geology, the Early Cretaceous high-Mg adakites in Luxi Terrane represent the magmatic response of intensive crust-mantle interaction caused by the underplating of voluminous mantle-derived magma in an extension intracontinental setting.","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136025441","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2023-09-11DOI: 10.2113/2023/lithosphere_2023_166
Lixia Feng, Baofu Han, Lin Wu, Zhongpeng Han, Jiawei Zhang, Mei Liu
Abstract The initial timing of extension during the Cenozoic around the northeastern margin of the Ordos Block, western North China Craton (NCC), is still poorly constrained. Apatite (U-Th)/He low-temperature thermochronology was thus applied on eight pre-Cenozoic granitic and gneissic samples transecting the eastern Daqingshan Mountains, northeastern margin of the Ordos Block, to investigate the denudation and cooling event related to the onset of extension therein. Four mean corrected AHe ages in the southern part are overlapped within the standard deviations of 50.0 ± 0.4 to 45.0 ± 8.0 Ma. However, three mean corrected AHe ages in the northern part are prominently older of 99.2 ± 11.0 to 86.6 ± 17.1 Ma, with the rest one of 56.1 ± 8.6 Ma. Altogether, they show a younger-older-younger-older pattern along the transect correlated with the normal faults. AHe thermal history modeling results further demonstrate extensive cooling during the Late Cretaceous but differential cooling during the Late Paleocene–Eocene. The Late Cretaceous extensive cooling in the eastern Daqingshan Mountains, as well as the contemporaneous deposition hiatus in both the eastern Daqingshan Mountains and the Hohhot Depression, together indicates overall denudation in the northeastern margin of the Ordos Block at that time. The Late Paleocene–Eocene differential cooling is probably induced by the tilting of the eastern Daqingshan Mountains as a result of the extension suggested by the distribution of AHe ages. It corresponds to the syn-tectonic subsidence in the Hohhot Depression, indicating a basin-mountain coupling. Regional comparative analysis manifests similar extension around the Ordos Block and more widely across the NCC during the Late Paleocene–Eocene. Temporally, kinematically, and dynamically coupled with this regional extension event, the subduction of the Izanagi-Pacific plate probably plays a major role. However, the contribution of the India-Asia collision could not be ignored.
{"title":"The Late Paleocene–Eocene Extension and Differential Denudation in the Eastern Daqingshan Mountains Around the Northeastern Margin of the Ordos Block, Western North China Craton, Constrained by Apatite (U-Th)/He Thermochronology","authors":"Lixia Feng, Baofu Han, Lin Wu, Zhongpeng Han, Jiawei Zhang, Mei Liu","doi":"10.2113/2023/lithosphere_2023_166","DOIUrl":"https://doi.org/10.2113/2023/lithosphere_2023_166","url":null,"abstract":"Abstract The initial timing of extension during the Cenozoic around the northeastern margin of the Ordos Block, western North China Craton (NCC), is still poorly constrained. Apatite (U-Th)/He low-temperature thermochronology was thus applied on eight pre-Cenozoic granitic and gneissic samples transecting the eastern Daqingshan Mountains, northeastern margin of the Ordos Block, to investigate the denudation and cooling event related to the onset of extension therein. Four mean corrected AHe ages in the southern part are overlapped within the standard deviations of 50.0 ± 0.4 to 45.0 ± 8.0 Ma. However, three mean corrected AHe ages in the northern part are prominently older of 99.2 ± 11.0 to 86.6 ± 17.1 Ma, with the rest one of 56.1 ± 8.6 Ma. Altogether, they show a younger-older-younger-older pattern along the transect correlated with the normal faults. AHe thermal history modeling results further demonstrate extensive cooling during the Late Cretaceous but differential cooling during the Late Paleocene–Eocene. The Late Cretaceous extensive cooling in the eastern Daqingshan Mountains, as well as the contemporaneous deposition hiatus in both the eastern Daqingshan Mountains and the Hohhot Depression, together indicates overall denudation in the northeastern margin of the Ordos Block at that time. The Late Paleocene–Eocene differential cooling is probably induced by the tilting of the eastern Daqingshan Mountains as a result of the extension suggested by the distribution of AHe ages. It corresponds to the syn-tectonic subsidence in the Hohhot Depression, indicating a basin-mountain coupling. Regional comparative analysis manifests similar extension around the Ordos Block and more widely across the NCC during the Late Paleocene–Eocene. Temporally, kinematically, and dynamically coupled with this regional extension event, the subduction of the Izanagi-Pacific plate probably plays a major role. However, the contribution of the India-Asia collision could not be ignored.","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136025440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Energy resources exploration has been taking place in the Southern North China Basin (SNCB) for decades, but no big breakthroughs have been made. A case study focusing on the Lower Permian Shanxi Formation in the Taikang Uplift of the SNCB is presented in this paper; based on the practice of shale gas exploration, we summarize the geological characteristics, geochemical characteristics, mineral characteristics, and pore type and analyze the exploration potential shale gas. The type of organic matter in the studied strata is mainly type III, the vitrinite reflectance (Ro) is between 2.1% and 3.4%, the average total organic carbon content is 1.66%, the mineral of shale is mainly composed of quartz and clay, and the main reservoir space types are mineral pores and microfractures. Through comprehensive evaluation, the sedimentary environment, organic matter abundance, physical properties, and mineral composition control the shale gas accumulation in the studied area.
{"title":"Geological Characteristics and Controlling Factors of Shale Gas in the Permian Shanxi Formation, the Southern North China Basin","authors":"Wei Wang, Qingshao Liang, Jingchun Tian, Xiang Zhang","doi":"10.2113/2023/1562420","DOIUrl":"https://doi.org/10.2113/2023/1562420","url":null,"abstract":"Abstract Energy resources exploration has been taking place in the Southern North China Basin (SNCB) for decades, but no big breakthroughs have been made. A case study focusing on the Lower Permian Shanxi Formation in the Taikang Uplift of the SNCB is presented in this paper; based on the practice of shale gas exploration, we summarize the geological characteristics, geochemical characteristics, mineral characteristics, and pore type and analyze the exploration potential shale gas. The type of organic matter in the studied strata is mainly type III, the vitrinite reflectance (Ro) is between 2.1% and 3.4%, the average total organic carbon content is 1.66%, the mineral of shale is mainly composed of quartz and clay, and the main reservoir space types are mineral pores and microfractures. Through comprehensive evaluation, the sedimentary environment, organic matter abundance, physical properties, and mineral composition control the shale gas accumulation in the studied area.","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136070130","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fault zones along active tectonic block boundaries are a significant source of devastating continental earthquakes. Strong earthquakes produce disruptions of sediment and induce characteristic sediments near the fault, which serve as valuable sedimentary evidence for identifying and dating of paleoearthquakes. In this study, we aimed to reconstruct the earthquake history of the Qilian–Haiyuan fault zone in the northeastern Tibetan Plateau during the Holocene. We reanalyzed forty-four trenches and used the sedimentary sequences, event indicators, and age constraints to determine the earthquake history. Our analysis revealed the paleoearthquakes of 6 subsidiary faults of the Qilian–Haiyuan fault zone with accurate event ages and rupture extents. Based on the spatial and temporal distributions of strong earthquakes since 10 ka, we identified five earthquake clusters around the central-eastern Qilian–Haiyuan fault zone including seven rupture cascades where the earthquakes migrated gradually from east to west. The existing seismic gap reveals that the latest migration may not yet be complete and suggests a high probability of M ≥ 7 earthquakes occurring on the Jinqianghe fault, Maomaoshan fault, and the central part of the Lenglongling faults. We concluded that, in order to better understand earthquake cycles and seismic hazards, it is important to consider a fault zone as a whole, including multiple faults and their interaction on the earthquake triggering between nearby faults.
{"title":"Holocene Earthquake Cycles of an Active Tectonic Block Boundary Fault Zone: A Case Study in the Qilian–Haiyuan Fault Zone, Northeastern Tibet Plateau","authors":"Shumin Liang, Wenjun Zheng, Dongli Zhang, Hui Peng, Xinzhe Sun, Shiqi Wei","doi":"10.2113/2023/7919174","DOIUrl":"https://doi.org/10.2113/2023/7919174","url":null,"abstract":"\u0000 Fault zones along active tectonic block boundaries are a significant source of devastating continental earthquakes. Strong earthquakes produce disruptions of sediment and induce characteristic sediments near the fault, which serve as valuable sedimentary evidence for identifying and dating of paleoearthquakes. In this study, we aimed to reconstruct the earthquake history of the Qilian–Haiyuan fault zone in the northeastern Tibetan Plateau during the Holocene. We reanalyzed forty-four trenches and used the sedimentary sequences, event indicators, and age constraints to determine the earthquake history. Our analysis revealed the paleoearthquakes of 6 subsidiary faults of the Qilian–Haiyuan fault zone with accurate event ages and rupture extents. Based on the spatial and temporal distributions of strong earthquakes since 10 ka, we identified five earthquake clusters around the central-eastern Qilian–Haiyuan fault zone including seven rupture cascades where the earthquakes migrated gradually from east to west. The existing seismic gap reveals that the latest migration may not yet be complete and suggests a high probability of M ≥ 7 earthquakes occurring on the Jinqianghe fault, Maomaoshan fault, and the central part of the Lenglongling faults. We concluded that, in order to better understand earthquake cycles and seismic hazards, it is important to consider a fault zone as a whole, including multiple faults and their interaction on the earthquake triggering between nearby faults.","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2023-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85959376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A low-crystallinity index chalcedony was found in the rhyolitic ignimbrite of the Late Jurassic Zhangjiakou Formation, located in Longhua County, Hebei Province, China. This chalcedony occurs as fillings along the fragile fractures of the host rock and is distinct from any other chalcedony deposits, such as the known basalt and carbonate-related types. The host rock is rhyolitic ignimbrite, comprising sanidine (50–70 vol.%), plagioclase (10–15 vol.%), quartz (8–10 vol.%), magnesian biotite (3–5 vol.%), and accessory minerals. The chalcedony appears as long lenticular veins and irregular-shaped bodies, occasionally containing small fragments of the surrounding rock at the boundary. It is colored in yellow, red, and/or white/colorless, with physical properties of specific gravity 2.55–2.56, reflection index of 1.54, Mohs hardness of 6.07–6.34, and weight loss of 1.97%–2.32% by heating. From the boundary to the inner center, its growth structure changes from comb-like macrocrystalline quartz to thin fiber crystallites and then to a relatively uniform cryptocrystalline phase, indicating precipitation from a crystalline to the cryptocrystalline sequence. Electron probe and Raman spectroscopy analyses reveal that the component minerals of the chalcedony are α-quartz and moganite and that the red inclusions are hematite. Quartz in chalcedony exhibits platelet shapes with tiny pores, which are cemented by nanograins, and such a structure is closer to that of opal. It’s crystallinity indexes (CIs) range ~1–3, as indicated by the X-ray diffraction patterns. This low CI and structural features, together with its occurrence, suggest a low temperature of 40°C–80°C during its formation. All these properties show a distinction from those of the most reported chalcedonies. This chalcedony is interpreted as an intermediate transitional type from normal chalcedony to opal, shedding new light on understanding microcrystalline silica mineral aggregate and exploration for a similar gem deposit.
{"title":"Low-Crystallinity Index Chalcedony from Longhua, China: Characteristics and Formation","authors":"Qiuli Yan, Guanghai Shi","doi":"10.2113/2023/2061776","DOIUrl":"https://doi.org/10.2113/2023/2061776","url":null,"abstract":"\u0000 A low-crystallinity index chalcedony was found in the rhyolitic ignimbrite of the Late Jurassic Zhangjiakou Formation, located in Longhua County, Hebei Province, China. This chalcedony occurs as fillings along the fragile fractures of the host rock and is distinct from any other chalcedony deposits, such as the known basalt and carbonate-related types. The host rock is rhyolitic ignimbrite, comprising sanidine (50–70 vol.%), plagioclase (10–15 vol.%), quartz (8–10 vol.%), magnesian biotite (3–5 vol.%), and accessory minerals. The chalcedony appears as long lenticular veins and irregular-shaped bodies, occasionally containing small fragments of the surrounding rock at the boundary. It is colored in yellow, red, and/or white/colorless, with physical properties of specific gravity 2.55–2.56, reflection index of 1.54, Mohs hardness of 6.07–6.34, and weight loss of 1.97%–2.32% by heating. From the boundary to the inner center, its growth structure changes from comb-like macrocrystalline quartz to thin fiber crystallites and then to a relatively uniform cryptocrystalline phase, indicating precipitation from a crystalline to the cryptocrystalline sequence. Electron probe and Raman spectroscopy analyses reveal that the component minerals of the chalcedony are α-quartz and moganite and that the red inclusions are hematite. Quartz in chalcedony exhibits platelet shapes with tiny pores, which are cemented by nanograins, and such a structure is closer to that of opal. It’s crystallinity indexes (CIs) range ~1–3, as indicated by the X-ray diffraction patterns. This low CI and structural features, together with its occurrence, suggest a low temperature of 40°C–80°C during its formation. All these properties show a distinction from those of the most reported chalcedonies. This chalcedony is interpreted as an intermediate transitional type from normal chalcedony to opal, shedding new light on understanding microcrystalline silica mineral aggregate and exploration for a similar gem deposit.","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2023-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87712507","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhenhua Xu, Shenghe Wu, Quanlin Wang, Pan Zhang, Meng Deng, W. Feng, Jiajia Zhang, Changmin Zhang
Digitate shallow-water deltas are commonly found in modern lakes and bays, as well as within cratonic petroliferous basins. They develop one or multiple sinuous finger-like sands (i.e., bar fingers), including high-RSI (sinuosity ratio of distributary channel and bar finger ≥1) and low-RSI (RSI < 1) types. Bar fingers consist of four types of subenvironments, that is, distributary channels, point bars, mouth bars, and levees. However, the internal architecture within the above subenvironments is still unclear. This paper documents the internal architecture of a digitate delta based on the integration of shallow-core and ground-penetrating radar data from the Ganjiang Delta, China, coupled with Delft3D simulations. Our results show that multiple convex-up muddy-silty accretion beds are developed in mouth bars, which top lap the side of the distributary channels or point bars and down lap the bottom of the mouth bar. The accretion beds have low dip angles (<2°), which is slightly higher for the upper accretion beds. Point bars, unique to the high-RSI bar finger, develop multiple inclined silty drapes, which top lap the top of the point bar. The cohesive levee and backwater effect impede the migration of the distributary channel, resulting in silty drapes with high-dip angles (can be >10°) compared with those in the supplying river. This dip angle exhibits a negative relationship with downstream distance and a positive exponential relationship with lateral migration distance. Silty drapes become dense along the migration direction of the distributary channel. The levee develops multiple horizontal muddy accretion beds. The high-RSI bar finger develops a large number (>3) of accretion beds in mouth bars with high dip angles, and a large number of accretion beds in thick levees, compared with the low-RSI bar finger. The results of this paper provide insights into the prediction and development of cratonic digitate shallow-water delta reservoirs.
{"title":"Internal Architectural Patterns of Bar Fingers Within Digitate Shallow-Water Delta: Insights from the Shallow Core, GPR and Delft3D Simulation Data of the Ganjiang Delta, China","authors":"Zhenhua Xu, Shenghe Wu, Quanlin Wang, Pan Zhang, Meng Deng, W. Feng, Jiajia Zhang, Changmin Zhang","doi":"10.2113/2022/9120724","DOIUrl":"https://doi.org/10.2113/2022/9120724","url":null,"abstract":"\u0000 Digitate shallow-water deltas are commonly found in modern lakes and bays, as well as within cratonic petroliferous basins. They develop one or multiple sinuous finger-like sands (i.e., bar fingers), including high-RSI (sinuosity ratio of distributary channel and bar finger ≥1) and low-RSI (RSI < 1) types. Bar fingers consist of four types of subenvironments, that is, distributary channels, point bars, mouth bars, and levees. However, the internal architecture within the above subenvironments is still unclear. This paper documents the internal architecture of a digitate delta based on the integration of shallow-core and ground-penetrating radar data from the Ganjiang Delta, China, coupled with Delft3D simulations. Our results show that multiple convex-up muddy-silty accretion beds are developed in mouth bars, which top lap the side of the distributary channels or point bars and down lap the bottom of the mouth bar. The accretion beds have low dip angles (<2°), which is slightly higher for the upper accretion beds. Point bars, unique to the high-RSI bar finger, develop multiple inclined silty drapes, which top lap the top of the point bar. The cohesive levee and backwater effect impede the migration of the distributary channel, resulting in silty drapes with high-dip angles (can be >10°) compared with those in the supplying river. This dip angle exhibits a negative relationship with downstream distance and a positive exponential relationship with lateral migration distance. Silty drapes become dense along the migration direction of the distributary channel. The levee develops multiple horizontal muddy accretion beds. The high-RSI bar finger develops a large number (>3) of accretion beds in mouth bars with high dip angles, and a large number of accretion beds in thick levees, compared with the low-RSI bar finger. The results of this paper provide insights into the prediction and development of cratonic digitate shallow-water delta reservoirs.","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87885227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lin Jiang, Wenfeng Zhao, Dongmei Bo, Yang Fan, Gang Zhou, Jiaqing Hao
We have witnessed a skyrocketing development of tight gas in China. However, all developed gas field in China face the obstacle of the decrease of production. The Xujiahe Formation in Sichuan Basin shows a promising future for the next big gas field. In this work, we will shed light on the densification mechanism and natural gas accumulation process of Triassic Xujiahe Formation, Hechuan Area, Sichuan Basin through physical experiments and theory analysis. We describe the reservoir characteristics. The diagenesis types and characteristics of sandstone reservoirs in the promising future of the next big gas field. In this work, we will shed light on the densification mechanism and natural gas accumulation process of Triassic Xujiahe Formation, Hechuan Area, Sichuan Basin through physical experiments and theory analysis. We describe the reservoir characteristics. The diagenesis types and characteristics of sandstone reservoirs in the second Member of Xujiahe Formation in Hechuan area are analyzed by means of rock thin section, cast thin section, and mercury injection. By observing the microscopic characteristics, types, and homogenization temperature distribution of fluid inclusions, the accumulation period of natural gas in Hechuan gas field is given, and the accumulation process of natural gas is revealed. The results show that (1) the natural gas charging the tight sandstone reservoirs of the Upper Triassic Xujiahe Formation in Hechuan area is a continuous process. The gas accumulation period can be roughly divided into two stages; (2) combining with the analysis of the hydrocarbon accumulation period of time, we put forward the natural gas accumulation model of the Xujiahe Formation, Hechuan area: the natural gas accumulation is accompanied by formation densification.
{"title":"Densification Mechanism and Natural Gas Accumulation Process, Triassic Xujiahe Formation, Hechuan Area, Sichuan Basin, China","authors":"Lin Jiang, Wenfeng Zhao, Dongmei Bo, Yang Fan, Gang Zhou, Jiaqing Hao","doi":"10.2113/2023/4522740","DOIUrl":"https://doi.org/10.2113/2023/4522740","url":null,"abstract":"\u0000 We have witnessed a skyrocketing development of tight gas in China. However, all developed gas field in China face the obstacle of the decrease of production. The Xujiahe Formation in Sichuan Basin shows a promising future for the next big gas field. In this work, we will shed light on the densification mechanism and natural gas accumulation process of Triassic Xujiahe Formation, Hechuan Area, Sichuan Basin through physical experiments and theory analysis. We describe the reservoir characteristics. The diagenesis types and characteristics of sandstone reservoirs in the promising future of the next big gas field. In this work, we will shed light on the densification mechanism and natural gas accumulation process of Triassic Xujiahe Formation, Hechuan Area, Sichuan Basin through physical experiments and theory analysis. We describe the reservoir characteristics. The diagenesis types and characteristics of sandstone reservoirs in the second Member of Xujiahe Formation in Hechuan area are analyzed by means of rock thin section, cast thin section, and mercury injection. By observing the microscopic characteristics, types, and homogenization temperature distribution of fluid inclusions, the accumulation period of natural gas in Hechuan gas field is given, and the accumulation process of natural gas is revealed. The results show that (1) the natural gas charging the tight sandstone reservoirs of the Upper Triassic Xujiahe Formation in Hechuan area is a continuous process. The gas accumulation period can be roughly divided into two stages; (2) combining with the analysis of the hydrocarbon accumulation period of time, we put forward the natural gas accumulation model of the Xujiahe Formation, Hechuan area: the natural gas accumulation is accompanied by formation densification.","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2023-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78080001","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Shrivastava, Mohammad B. Raza, L. Saha, K. Yi, P. Nasipuri, J. Pati
In this article, novel geochronological (U–Pb SHRIMP) and geochemical data are presented from the lowermost sandstone unit (Par formation), basement granites of Gwalior Basin and sandstones from the Bhopal Basin, located along margins of the Archaean Bundelkhand Craton. The geochemical variation diagrams imply that sandstone units in the Gwalior and Bhopal Basins were deposited in rift-induced passive margin tectonic settings. In contrast to the magmatic features that are preserved in the zircons of granite of the Gwalior Basins, detrital zircons from sandstones of both basins are fragmentary and polymodal in size. The magmatic zircon grains from the basement granites yield a 207Pb/206Pb concordant age of 2538 ± 2 Ma. A group of detrital zircons from the sandstone of the Gwalior Basin with concentric magmatic zonation yield a weighted mean average age of 2564 ± 24 Ma. The detrital zircons from Gwalior Basin exhibit a patchy U-Th distribution overgrowing the magmatic zonation yield average age of 2044 ± 2 Ma. The detrital zircons from the Bhopal basin yield three distinct concordant ages of 2511 ± 5, 1694 ± 6, and 1355±9 Ma. The presence of ~2540 Ma concordant zircon population with concentric zonation in the sandstone of Bhopal Basin suggests their derivation from the granite of similar age. Therefore, an extension of Bundelkhand Craton granite below the Bhopal Basin is suggested. The 2500 Ma ages from the Gwalior granites are linked to global magmatic activity leading to the stabilization of extended Ur at ~2500 Ma. The 2048 and 1355 Ma ages from the Gwalior and Bhopal Basins, respectively, are concluded as the maximum depositional age (MDA) of the lowermost stratigraphic units within the basins. The MDAs are concluded to be the timings of passive margin basin formations along margins of the Bundelkhand Craton during extended Ur and Nuna or Columbia disintegration, respectively, during plume-driven tectonics.
{"title":"Paleo-Mesoproterozoic Rifting Along the Margins of Archean Bundelkhand Craton North-Central India: Timing the Event from U–Pb SHRIMP Zircon Data and Their Geodynamic Implications","authors":"A. Shrivastava, Mohammad B. Raza, L. Saha, K. Yi, P. Nasipuri, J. Pati","doi":"10.2113/2023/4111013","DOIUrl":"https://doi.org/10.2113/2023/4111013","url":null,"abstract":"\u0000 In this article, novel geochronological (U–Pb SHRIMP) and geochemical data are presented from the lowermost sandstone unit (Par formation), basement granites of Gwalior Basin and sandstones from the Bhopal Basin, located along margins of the Archaean Bundelkhand Craton. The geochemical variation diagrams imply that sandstone units in the Gwalior and Bhopal Basins were deposited in rift-induced passive margin tectonic settings. In contrast to the magmatic features that are preserved in the zircons of granite of the Gwalior Basins, detrital zircons from sandstones of both basins are fragmentary and polymodal in size. The magmatic zircon grains from the basement granites yield a 207Pb/206Pb concordant age of 2538 ± 2 Ma. A group of detrital zircons from the sandstone of the Gwalior Basin with concentric magmatic zonation yield a weighted mean average age of 2564 ± 24 Ma. The detrital zircons from Gwalior Basin exhibit a patchy U-Th distribution overgrowing the magmatic zonation yield average age of 2044 ± 2 Ma. The detrital zircons from the Bhopal basin yield three distinct concordant ages of 2511 ± 5, 1694 ± 6, and 1355±9 Ma. The presence of ~2540 Ma concordant zircon population with concentric zonation in the sandstone of Bhopal Basin suggests their derivation from the granite of similar age. Therefore, an extension of Bundelkhand Craton granite below the Bhopal Basin is suggested. The 2500 Ma ages from the Gwalior granites are linked to global magmatic activity leading to the stabilization of extended Ur at ~2500 Ma. The 2048 and 1355 Ma ages from the Gwalior and Bhopal Basins, respectively, are concluded as the maximum depositional age (MDA) of the lowermost stratigraphic units within the basins. The MDAs are concluded to be the timings of passive margin basin formations along margins of the Bundelkhand Craton during extended Ur and Nuna or Columbia disintegration, respectively, during plume-driven tectonics.","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2023-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88031538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Min Wu, Jiyuan Yin, Zhiyuan He, W. Xiao, Yannan Wang, Wen Chen, Yamei Wang, Jingbo Sun, Dapeng Li, Yun Meng
The Meso-Cenozoic tectonic activities of the Central Asian Orogenic Belt (CAOB) played an important role in controlling the present-day topography of Central Asia. The Altai orogenic belt is a key component in the southern CAOB; so far, there is still a lack of sufficient constraints on the time and mechanism of its tectonic reactivation since the Mesozoic. In this contribution, we present new zircon and apatite (U-Th)/He and apatite fission track thermochronological data from granitoid samples in the Habahe area, western Altai orogenic belt. Therein zircon (U-Th)/He ages range from ~230 to ~238 Ma, apatite fission track central ages are ~140–157 Ma, and apatite (U-Th)/He ages vary from ~134 to ~149 Ma. Based on the associated thermal history modeling results, the Habahe area underwent a moderate cooling during the Late Triassic to Middle Jurassic (~230–170 Ma) with a cooling rate of ~0.8–1.1℃/Ma and a subsequent moderate to slightly rapid cooling stage during the Middle Jurassic to Early Cretaceous (170–130 Ma) with a cooling rate of ~1.5–2.3℃/Ma. We propose that this prolonged cooling stage occurred under a long-lasting contractional tectonism in the western Altai throughout the early Mesozoic, which was produced by multiplate convergence in East Asia during this period, mainly including the consumption of the Mongol-Okhotsk Ocean in the northeast and the Meso-Tethys Ocean in the south. The region experienced rather limited Late Cretaceous-Cenozoic cooling and exhumation due to insufficient reactivation and weak surficial erosion.
{"title":"Mesozoic Thermo-Tectonic Evolution of the Western Altai Orogenic Belt (NW China): Insights from Low-Temperature Thermochronology","authors":"Min Wu, Jiyuan Yin, Zhiyuan He, W. Xiao, Yannan Wang, Wen Chen, Yamei Wang, Jingbo Sun, Dapeng Li, Yun Meng","doi":"10.2113/2023/8161000","DOIUrl":"https://doi.org/10.2113/2023/8161000","url":null,"abstract":"\u0000 The Meso-Cenozoic tectonic activities of the Central Asian Orogenic Belt (CAOB) played an important role in controlling the present-day topography of Central Asia. The Altai orogenic belt is a key component in the southern CAOB; so far, there is still a lack of sufficient constraints on the time and mechanism of its tectonic reactivation since the Mesozoic. In this contribution, we present new zircon and apatite (U-Th)/He and apatite fission track thermochronological data from granitoid samples in the Habahe area, western Altai orogenic belt. Therein zircon (U-Th)/He ages range from ~230 to ~238 Ma, apatite fission track central ages are ~140–157 Ma, and apatite (U-Th)/He ages vary from ~134 to ~149 Ma. Based on the associated thermal history modeling results, the Habahe area underwent a moderate cooling during the Late Triassic to Middle Jurassic (~230–170 Ma) with a cooling rate of ~0.8–1.1℃/Ma and a subsequent moderate to slightly rapid cooling stage during the Middle Jurassic to Early Cretaceous (170–130 Ma) with a cooling rate of ~1.5–2.3℃/Ma. We propose that this prolonged cooling stage occurred under a long-lasting contractional tectonism in the western Altai throughout the early Mesozoic, which was produced by multiplate convergence in East Asia during this period, mainly including the consumption of the Mongol-Okhotsk Ocean in the northeast and the Meso-Tethys Ocean in the south. The region experienced rather limited Late Cretaceous-Cenozoic cooling and exhumation due to insufficient reactivation and weak surficial erosion.","PeriodicalId":18147,"journal":{"name":"Lithosphere","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2023-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77242714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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