2014 Vol. 39, No. 8
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2014, 39(8): 915-928.
doi: 10.3799/dqkx.2014.086
Abstract:
Sedimentary tectonic facies reveals different types of sedimentary basins and their sequences, distribution and comprehensive combination formed in a tectonic setting of a specific tectonic site in each evolutionary stage during the formation and evolution of a continental block, an ocean or a continental margin (active or passive), which is an integrated product of dynamic processes of divergence, convergence, collision and rotation-shear of continental lithosphere plates as well. It has the function of revealing the formation and evolution of continental blocks and orogenic systems (belts). In order to systematically analyze the complicated process of continental accretion since Neoproterozoic in Mainland China in the perspective of sedimentary tectonic facies and sedimentary basins based on characteristics of formation and evolution in Mainland China, this paper puts forward a set of classification scheme and briefly introduces identification markers of sedimentary tectonic facies (types of sedimentary basins). The scheme can be divided into 4 levels (facies series, macrofacies, facies and subfacies): the first level is continental block (including land block) and orogenic system facies series. Thereinto, continental block can be divided into macrofacies and facies on the basis of tectonic paleogeographic site and regional tectonic stress field. The orogenic system is comprised of arc-basin systems, accretional zone and opposite zone, with huge mountains accompanied by complex lithologic composition, fold and fault. In fact, it is the outcome of arc accretion, arc-arc collision, arc-continent collision, continent-continent collision, and inter-continent subduction in the process of conversion between continent and ocean, under the extensive act of horizontal movement of lithosphere plate. The accretional zone is the product of soft collision controlled by arc-arc and arc-continental collision, which spreads across the ocean-continent transformation accretion zone in continental margin. In contrast, the opposite zone is the outcome of hard collision formed by continent-continent collision. Down to next level, we can divide sedimentary tectonic basins into oceanic basin, forearc bsin, interarc basin, backarc basin, residue sea, peripheral foreland basin, backarc foreland basin, and so on, according to a series of tectonic paleogeographical environment and construction generated by the progress of ocean-continent transformation.
Sedimentary tectonic facies reveals different types of sedimentary basins and their sequences, distribution and comprehensive combination formed in a tectonic setting of a specific tectonic site in each evolutionary stage during the formation and evolution of a continental block, an ocean or a continental margin (active or passive), which is an integrated product of dynamic processes of divergence, convergence, collision and rotation-shear of continental lithosphere plates as well. It has the function of revealing the formation and evolution of continental blocks and orogenic systems (belts). In order to systematically analyze the complicated process of continental accretion since Neoproterozoic in Mainland China in the perspective of sedimentary tectonic facies and sedimentary basins based on characteristics of formation and evolution in Mainland China, this paper puts forward a set of classification scheme and briefly introduces identification markers of sedimentary tectonic facies (types of sedimentary basins). The scheme can be divided into 4 levels (facies series, macrofacies, facies and subfacies): the first level is continental block (including land block) and orogenic system facies series. Thereinto, continental block can be divided into macrofacies and facies on the basis of tectonic paleogeographic site and regional tectonic stress field. The orogenic system is comprised of arc-basin systems, accretional zone and opposite zone, with huge mountains accompanied by complex lithologic composition, fold and fault. In fact, it is the outcome of arc accretion, arc-arc collision, arc-continent collision, continent-continent collision, and inter-continent subduction in the process of conversion between continent and ocean, under the extensive act of horizontal movement of lithosphere plate. The accretional zone is the product of soft collision controlled by arc-arc and arc-continental collision, which spreads across the ocean-continent transformation accretion zone in continental margin. In contrast, the opposite zone is the outcome of hard collision formed by continent-continent collision. Down to next level, we can divide sedimentary tectonic basins into oceanic basin, forearc bsin, interarc basin, backarc basin, residue sea, peripheral foreland basin, backarc foreland basin, and so on, according to a series of tectonic paleogeographical environment and construction generated by the progress of ocean-continent transformation.
2014, 39(8): 929-953.
doi: 10.3799/dqkx.2014.087
Abstract:
This paper firstly analyzes the lithological features, the thickness of sequence, metamorphical features and the sedimentary environment of seven Nanhuan-Permian combined sections from South China, then analyzes the petrological assemblages including ophiolites, basalts, island arc igneous and the TTG-GG suites (granites) from the area of south margin of Yangtze continental block and the area of Cathay accreting block and lastly analyzes the basin features based on the lithology of each unit (formation) from South China. Based on the above-mentioned analyses, four stages of tectonic evolution of South China are identified and it is concluded that the collision between the Yangtze continental block and Cathay accreting block occurred at the end of the Early Paleozoic along the northeastern part and the collision along the southwestern part occurred at the end of the Permian.
This paper firstly analyzes the lithological features, the thickness of sequence, metamorphical features and the sedimentary environment of seven Nanhuan-Permian combined sections from South China, then analyzes the petrological assemblages including ophiolites, basalts, island arc igneous and the TTG-GG suites (granites) from the area of south margin of Yangtze continental block and the area of Cathay accreting block and lastly analyzes the basin features based on the lithology of each unit (formation) from South China. Based on the above-mentioned analyses, four stages of tectonic evolution of South China are identified and it is concluded that the collision between the Yangtze continental block and Cathay accreting block occurred at the end of the Early Paleozoic along the northeastern part and the collision along the southwestern part occurred at the end of the Permian.
2014, 39(8): 954-976.
doi: 10.3799/dqkx.2014.088
Abstract:
Based on the comprehensive analysis of the sedimentary basin distribution, filling sequences, lithofacies palaeogeography in the three periods of T1-2, T3-J1, J2-K in Mesozoic, the spatiotemporal revolution characteristics of the sedimentary basins during Mesozoic are summarized, the response relationship between the tectonic movement and the space-time revolution of the sedimentary basins during Mesozoic are discussed. And the conclusions as follows are drawn. (1) Along with the subduction of the Paleo-Asia ocean and the forming of the Tianshan-Xingmeng orogenic belt, the northern China was generally in a stage of landmass collision, and the basin-mountain pattern of northwest area also basically finalizes. In the south, a series of back arc oceanic basins in the north Qiangtang-Sanjiang archipelagic arc-basin system died off successively results from the two-way subduction of the Paleo-Tethys ocean. (2)The Indosinian movement in Late Triassic made the Paleo-Asia come to final solidification and outward expansion, and large-scale regression in south made most areas in China enter an intracontinental evolution phase. After the Indosinian movement, the west paleo-Mediterranean region and the east Paleo-Pacific were separated by the uplift of the central South China. (3) Since Middle Jurassic, the whole eastern China was involved in Pacific tectonic process, and the active continental margin of West Pacific Ocean formed affected by the Pacific Plate sliding beneath the Eurasian Plate. Most of the Northeast China developed iintra-arc rift (volcanic sedimentary) basin, while the North China continental block and the Alashan land block became divided. The mid-west area mainly consists of compressional basins, rift basins or depression basins, and the east developed intra-arc rift basins of epicontinental magma arc.In South China, drawing the Xuefeng Mountain as borderline, the east also developed iintra-arc rift basins related to the evolution of epicontinental magma arc, while the west developed large intracontinental compressional basins, rift basins or depression basins. The southwest area was still in a archipelagic arc-basin system pattern.
Based on the comprehensive analysis of the sedimentary basin distribution, filling sequences, lithofacies palaeogeography in the three periods of T1-2, T3-J1, J2-K in Mesozoic, the spatiotemporal revolution characteristics of the sedimentary basins during Mesozoic are summarized, the response relationship between the tectonic movement and the space-time revolution of the sedimentary basins during Mesozoic are discussed. And the conclusions as follows are drawn. (1) Along with the subduction of the Paleo-Asia ocean and the forming of the Tianshan-Xingmeng orogenic belt, the northern China was generally in a stage of landmass collision, and the basin-mountain pattern of northwest area also basically finalizes. In the south, a series of back arc oceanic basins in the north Qiangtang-Sanjiang archipelagic arc-basin system died off successively results from the two-way subduction of the Paleo-Tethys ocean. (2)The Indosinian movement in Late Triassic made the Paleo-Asia come to final solidification and outward expansion, and large-scale regression in south made most areas in China enter an intracontinental evolution phase. After the Indosinian movement, the west paleo-Mediterranean region and the east Paleo-Pacific were separated by the uplift of the central South China. (3) Since Middle Jurassic, the whole eastern China was involved in Pacific tectonic process, and the active continental margin of West Pacific Ocean formed affected by the Pacific Plate sliding beneath the Eurasian Plate. Most of the Northeast China developed iintra-arc rift (volcanic sedimentary) basin, while the North China continental block and the Alashan land block became divided. The mid-west area mainly consists of compressional basins, rift basins or depression basins, and the east developed intra-arc rift basins of epicontinental magma arc.In South China, drawing the Xuefeng Mountain as borderline, the east also developed iintra-arc rift basins related to the evolution of epicontinental magma arc, while the west developed large intracontinental compressional basins, rift basins or depression basins. The southwest area was still in a archipelagic arc-basin system pattern.
2014, 39(8): 977-986.
doi: 10.3799/dqkx.2014.089
Abstract:
The Huayuan ore concentration area in the western Hunan Province, located in transitional zone between the southeastern margin of Yangtze block and the Xuefeng (Jiangnan) orogenic belt, is important section of the Xiangxi-Exi metallogenetic belt, and is the only one which occurs in limestone of Lower Cambrian strata in the Yangtze block. The Shizishan Pb-Zn deposit which was one of recently discovered Pb-Zn deposits in Xiangxi-Exi metallogenetic belt is located in the center of the Huayuan ore concentration area, and its main ore bodies occur in stratoid with the same trending as the strata and are sharply bounded by wall rocks with weak hydrothermal alteration such as calcitization. Ore bodies are strictly controlled by algal limestone of the third section of the lower member of the Lower Cambrian Qingxudong Formation. Ore minerals are mainly sphalerite, and a small amount of galena and pyrite, whereas gangue mineral is mainly calcite, and a small amount of barite and fluorite. Using the total-sample-dissolution method and leaching method to sphalerite in the Shizishan Pb-Zn deposit for Rb-Sr isochron dating. The isochron ages are obtained 410±12 Ma (MSWD=2.20) with initial 87Sr/86Sr value of 0.709 16 for mineral-phase+residue phase, which shows that the Early Devonian is the main time for the formation of the Shizishan Pb-Zn deposit. Research results indicate that the formation of the deposit is probably related to the regional migration of the basin fluid when the crust is stretched behind the Late Caledonian tectonic movement in Early Devonian, and the age is also a constraint on the Pb-Zn ore-forming time of the whole Huayuan ore concentration area. The initial 87Sr/86Sr value of the mineral phase+residue phase is 0.709 16, which is slightly higher than those of the ore-bearing limestone, and close to those of the overlying dolostone of Middle-Upper Cambrian strata, indicating that the ore-forming materials of the ore bodies in the Shizishan Pb-Zn deposit are possibly derived from the overlying dolostone strata. It is thus concluded that direct dating of the ages of metal minerals by using Rb-Sr isochron method for single minerals and mineral residues could serve as a routine dating method.
The Huayuan ore concentration area in the western Hunan Province, located in transitional zone between the southeastern margin of Yangtze block and the Xuefeng (Jiangnan) orogenic belt, is important section of the Xiangxi-Exi metallogenetic belt, and is the only one which occurs in limestone of Lower Cambrian strata in the Yangtze block. The Shizishan Pb-Zn deposit which was one of recently discovered Pb-Zn deposits in Xiangxi-Exi metallogenetic belt is located in the center of the Huayuan ore concentration area, and its main ore bodies occur in stratoid with the same trending as the strata and are sharply bounded by wall rocks with weak hydrothermal alteration such as calcitization. Ore bodies are strictly controlled by algal limestone of the third section of the lower member of the Lower Cambrian Qingxudong Formation. Ore minerals are mainly sphalerite, and a small amount of galena and pyrite, whereas gangue mineral is mainly calcite, and a small amount of barite and fluorite. Using the total-sample-dissolution method and leaching method to sphalerite in the Shizishan Pb-Zn deposit for Rb-Sr isochron dating. The isochron ages are obtained 410±12 Ma (MSWD=2.20) with initial 87Sr/86Sr value of 0.709 16 for mineral-phase+residue phase, which shows that the Early Devonian is the main time for the formation of the Shizishan Pb-Zn deposit. Research results indicate that the formation of the deposit is probably related to the regional migration of the basin fluid when the crust is stretched behind the Late Caledonian tectonic movement in Early Devonian, and the age is also a constraint on the Pb-Zn ore-forming time of the whole Huayuan ore concentration area. The initial 87Sr/86Sr value of the mineral phase+residue phase is 0.709 16, which is slightly higher than those of the ore-bearing limestone, and close to those of the overlying dolostone of Middle-Upper Cambrian strata, indicating that the ore-forming materials of the ore bodies in the Shizishan Pb-Zn deposit are possibly derived from the overlying dolostone strata. It is thus concluded that direct dating of the ages of metal minerals by using Rb-Sr isochron method for single minerals and mineral residues could serve as a routine dating method.
2014, 39(8): 987-999.
doi: 10.3799/dqkx.2014.090
Abstract:
West Kunlun orogenic belt is located in the northwest margin of the Qinghai-Tibet Plateau, and in the southwest edge of Tarim basin. This belt is an important part of the central orogenic belt. It has experienced a long and complicated tectonic-sedimentary evolution. This paper presents lithostratigraphy of outcrops in five stratigraphic subregions and their corresponding sedimentary basin types in West Kunlun orogenic belt. The evolutionary history of sedimentary basins in West Kunlun is explored and divided into following three stages from Neoproterozoic to Mesozoic in this study: (1) the stage of continental break-up and the formation of oceanic crust in Neoproterozoic; (2) the stage of plate mechanism evolution in Early Paleozoic-Middle Triassic; (3) the stage of evolution in intracontinental since Late Triassic.
West Kunlun orogenic belt is located in the northwest margin of the Qinghai-Tibet Plateau, and in the southwest edge of Tarim basin. This belt is an important part of the central orogenic belt. It has experienced a long and complicated tectonic-sedimentary evolution. This paper presents lithostratigraphy of outcrops in five stratigraphic subregions and their corresponding sedimentary basin types in West Kunlun orogenic belt. The evolutionary history of sedimentary basins in West Kunlun is explored and divided into following three stages from Neoproterozoic to Mesozoic in this study: (1) the stage of continental break-up and the formation of oceanic crust in Neoproterozoic; (2) the stage of plate mechanism evolution in Early Paleozoic-Middle Triassic; (3) the stage of evolution in intracontinental since Late Triassic.
2014, 39(8): 1000-1016.
doi: 10.3799/dqkx.2014.091
Abstract:
Qilian-Qaidam-East Kunlun area, located at the mid-western of the Central Orogenic Belt, has a complicated tectonic history. The tectonic-sedimentary evolution is discussed based on its sedimentary characteristics in this paper. During Neoproterozoic to Early Paleozoic, North Qilian Ocean, Saishiteng-Xitieshan Ocean, and East Kunlun Ocean opened, the study area developed continental-margin rift and ocean basin deposition. At the end of Early Paleozoic, foreland basin, continental-margin graben developed following the successive closing of the three oceans. From Cambrian to Early Triassic, A'nyemaqen Ocean completed an opening-closing cycle, and the study area began the phase of inland fault basin, downwarped basin deposits. The opening-closing cycles of ocean and intracontinent orogen are recorded in deposits of the study area, which provides sedimentary evidence for the above tectonic event.
Qilian-Qaidam-East Kunlun area, located at the mid-western of the Central Orogenic Belt, has a complicated tectonic history. The tectonic-sedimentary evolution is discussed based on its sedimentary characteristics in this paper. During Neoproterozoic to Early Paleozoic, North Qilian Ocean, Saishiteng-Xitieshan Ocean, and East Kunlun Ocean opened, the study area developed continental-margin rift and ocean basin deposition. At the end of Early Paleozoic, foreland basin, continental-margin graben developed following the successive closing of the three oceans. From Cambrian to Early Triassic, A'nyemaqen Ocean completed an opening-closing cycle, and the study area began the phase of inland fault basin, downwarped basin deposits. The opening-closing cycles of ocean and intracontinent orogen are recorded in deposits of the study area, which provides sedimentary evidence for the above tectonic event.
2014, 39(8): 1017-1034.
doi: 10.3799/dqkx.2014.092
Abstract:
The Lower Yangtze continent formed during Mesozoic is divided into 5 types of sedimentary basin with different time frames, namely, epeiric sea (T1-2), peripheral foreland basin(T3-J1), pressurized basin(T3-J2), fault-depression basin(J3-K), and pull apart basin (J3-K) in this paper based on the study of lithostratigraphy, sedimentary formation, biostratigraphic and chronostratigraphic correlation, prototype basin, basin filling sequences, and comprehensive lithofacies paleogeographic analysis of the study area in addition. The space distribution framework of Mesozoic Lower Yangtze continental sedimentary basin is established, and the tectonic environment evolution is discussed. It is found that the Triassic-Early Jurassic tectonic phase is related to the evolution of Tethys Sea, which can be divided into two sub-phases of Early-Middle Triassic epeiric sea and Late Triassic foreland basin. The Jurassic-Cretaceous phase transformed to Peri-Pacific tectonic domain can be divided into two sub-phases. Early-Middle Jurassic dominated by compressive tectonic background mainly developed the uplift and erosion areas, whereas Late Jurassic-Cretaceous characterized by an extensional tectonic environment developed a series of NE volcanic-sedimentary fault-depression basin and pull apart basin, which in turn formed basin-range tectonic framework.
The Lower Yangtze continent formed during Mesozoic is divided into 5 types of sedimentary basin with different time frames, namely, epeiric sea (T1-2), peripheral foreland basin(T3-J1), pressurized basin(T3-J2), fault-depression basin(J3-K), and pull apart basin (J3-K) in this paper based on the study of lithostratigraphy, sedimentary formation, biostratigraphic and chronostratigraphic correlation, prototype basin, basin filling sequences, and comprehensive lithofacies paleogeographic analysis of the study area in addition. The space distribution framework of Mesozoic Lower Yangtze continental sedimentary basin is established, and the tectonic environment evolution is discussed. It is found that the Triassic-Early Jurassic tectonic phase is related to the evolution of Tethys Sea, which can be divided into two sub-phases of Early-Middle Triassic epeiric sea and Late Triassic foreland basin. The Jurassic-Cretaceous phase transformed to Peri-Pacific tectonic domain can be divided into two sub-phases. Early-Middle Jurassic dominated by compressive tectonic background mainly developed the uplift and erosion areas, whereas Late Jurassic-Cretaceous characterized by an extensional tectonic environment developed a series of NE volcanic-sedimentary fault-depression basin and pull apart basin, which in turn formed basin-range tectonic framework.
2014, 39(8): 1140-1154.
doi: 10.3799/dqkx.2014.100
Abstract:
In order to study the sendimentary basin evolution of the Wuyi-Yunkai area, in this paper the area is divided into 5 stratigraphic regions. Based on the previous studies on the lithostritagraphy combinations, fossil assemblages, isotopic geochronology and tectonics of this area, types of sedimentary basin in the Wuyi-Yunkai area are identified, and their formation and evolution are investigated. The evolutional history of the sedimentary and tectonic features of the study area shows that the basin and structure have experienced three major evolutionary stages in Mesozoic. In the Early-Middle Triassic, the research area entered the marine-continental alternating epicontinental sea stage because of transgressions with the crust uplifting, the main sea level dropping and the sea gradually receding to the west or southwest. In the Middle Jurassic-Cretaceous, a series of subduction-accretionary complex belt formed in Taiwan, and inland areas were bounded by the Zhenghe-Dapu fracture, with fault basin (including volcanoes) developed in the west and its east entering evolutionary stage of intra-arc graben basin whose late stage was fault basin evolution, mainly influenced by the low subduction of the Pacific plate.
In order to study the sendimentary basin evolution of the Wuyi-Yunkai area, in this paper the area is divided into 5 stratigraphic regions. Based on the previous studies on the lithostritagraphy combinations, fossil assemblages, isotopic geochronology and tectonics of this area, types of sedimentary basin in the Wuyi-Yunkai area are identified, and their formation and evolution are investigated. The evolutional history of the sedimentary and tectonic features of the study area shows that the basin and structure have experienced three major evolutionary stages in Mesozoic. In the Early-Middle Triassic, the research area entered the marine-continental alternating epicontinental sea stage because of transgressions with the crust uplifting, the main sea level dropping and the sea gradually receding to the west or southwest. In the Middle Jurassic-Cretaceous, a series of subduction-accretionary complex belt formed in Taiwan, and inland areas were bounded by the Zhenghe-Dapu fracture, with fault basin (including volcanoes) developed in the west and its east entering evolutionary stage of intra-arc graben basin whose late stage was fault basin evolution, mainly influenced by the low subduction of the Pacific plate.
2014, 39(8): 1155-1168.
doi: 10.3799/dqkx.2014.101
Abstract:
Based on comprehensive analysis of the type, sedimentary formation, biostratigraphy and chronostratigraphy for 24 main sedimentary basins, we study the evolution of sedimentary basins of Xing-Meng orogenic belt in the Neoproterozoic-Paleozoic, dividing it into six phases as follows. (1) The epicontinental accretion in the Neoproterozoic to Early Cambrian characterized by the assembly of Ergun and Xing'an blocks, as Huanyu-Xinlin ophiolite accreted to margin of southern Ergun blocks; (2) The stable epicontinental sediment in the Terreneuvian-Serises 2, with the feature of a relatively stable clastic-calciclastic sediment around the blocks while Jiamusi massif affected by Late Pan-African metamorphic event; (3) The formation of archipelagic arc-basin systems in the Early and Middle Ordovician, marked by the distribution of arc-basin in the margin of Duobaoshan and the different levels oceanic crust subduction effect among other land masses; (4) The development of archipelagic arc-basin systems in the Late Ordovician to Pridoli, as the erosion of the uplifted land masses; (5) The subduction of archipelagic arc-basin systems in the Early Devonian to Early Carboniferous, characterized by the collage of Ergun-Xing'an and Songnen blocks and the transformation of western margin of Jiamusi massif from passive to active in the late Early Carboniferous; (6) The oceanic-continental transition in the Late Carboniferous-Lopingian, characterized by the assembly of Jiamusi massif, Songnen massif, and Khanka massif. Massifs of Northeast China completely collaged to a whole.
Based on comprehensive analysis of the type, sedimentary formation, biostratigraphy and chronostratigraphy for 24 main sedimentary basins, we study the evolution of sedimentary basins of Xing-Meng orogenic belt in the Neoproterozoic-Paleozoic, dividing it into six phases as follows. (1) The epicontinental accretion in the Neoproterozoic to Early Cambrian characterized by the assembly of Ergun and Xing'an blocks, as Huanyu-Xinlin ophiolite accreted to margin of southern Ergun blocks; (2) The stable epicontinental sediment in the Terreneuvian-Serises 2, with the feature of a relatively stable clastic-calciclastic sediment around the blocks while Jiamusi massif affected by Late Pan-African metamorphic event; (3) The formation of archipelagic arc-basin systems in the Early and Middle Ordovician, marked by the distribution of arc-basin in the margin of Duobaoshan and the different levels oceanic crust subduction effect among other land masses; (4) The development of archipelagic arc-basin systems in the Late Ordovician to Pridoli, as the erosion of the uplifted land masses; (5) The subduction of archipelagic arc-basin systems in the Early Devonian to Early Carboniferous, characterized by the collage of Ergun-Xing'an and Songnen blocks and the transformation of western margin of Jiamusi massif from passive to active in the late Early Carboniferous; (6) The oceanic-continental transition in the Late Carboniferous-Lopingian, characterized by the assembly of Jiamusi massif, Songnen massif, and Khanka massif. Massifs of Northeast China completely collaged to a whole.
2014, 39(8): 1169-1184.
doi: 10.3799/dqkx.2014.102
Abstract:
In the light of the stratigraphic framework, the authors collected and summarized evidences of the rock formations and their ages in the sedimentary basins of the Bangonghu-Shuanghu-Nujiang-Changning-Menglian suture zone. With the guidance of the plate tectonic theory and continental dynamics, the basin types are also classified in the study area to explore the temporal and spatial evolution of the basins and to better the understanding of the opening, extension and closing of the Paleo-Tethys oceans. Four evolutional stages of the Pre-Cenozoic Paleo-Tethys oceans corresponding to the basinal evolution in the study area are distinguished. It is found that Ordovician ophiolitic mélange of MORB characteristics occurred in both the Longmu-Shuanghu and the Changning-Menglian oceanic basin, two of which prove to have experienced arc-continent collision during the end Permian-Early Triassic transition, suggesting a united remnant oceanic basin of the Paleo-Tethys. The remnant Paleo-Tethys represented by the Bangonghu-Nujiang oceanic basin, on the other hand, opened in the Early Carboniferous and evolved to a closure in the Early Cretaceous, marking the final disappearance of the Paleo-Tethys.
In the light of the stratigraphic framework, the authors collected and summarized evidences of the rock formations and their ages in the sedimentary basins of the Bangonghu-Shuanghu-Nujiang-Changning-Menglian suture zone. With the guidance of the plate tectonic theory and continental dynamics, the basin types are also classified in the study area to explore the temporal and spatial evolution of the basins and to better the understanding of the opening, extension and closing of the Paleo-Tethys oceans. Four evolutional stages of the Pre-Cenozoic Paleo-Tethys oceans corresponding to the basinal evolution in the study area are distinguished. It is found that Ordovician ophiolitic mélange of MORB characteristics occurred in both the Longmu-Shuanghu and the Changning-Menglian oceanic basin, two of which prove to have experienced arc-continent collision during the end Permian-Early Triassic transition, suggesting a united remnant oceanic basin of the Paleo-Tethys. The remnant Paleo-Tethys represented by the Bangonghu-Nujiang oceanic basin, on the other hand, opened in the Early Carboniferous and evolved to a closure in the Early Cretaceous, marking the final disappearance of the Paleo-Tethys.
2014, 39(8): 1185-1199.
doi: 10.3799/dqkx.2014.103
Abstract:
As the eastern part of the Central Orogenic Belt, Qinling-Dabie Orogenic Belt has a complicated tectonic-sedimentary history. On the basis of a systematic research on the lithostratigraphy, fossil assemblages, isotopic geochronology and tectonics of 4 secondary and 13 three-level tectonic units, this paper divides the study area into 18 types of sedimentary basins, and discusses its tectonic-sedimentary evolution from Neoproterozoic to Mesozoic: (1) Neoproterozoic-Early Paleozoic: North Qinling was magmatic arc and forearc basin; South Qinling experienced intracontinental rift to interplatform basin-platform to continental-margin rift; Dabie-Sulu experienced intracontinental rift to interplatform basin-platform. (2) Late Paleozoic: North Qinling was marine-continental alternation epeiric sea; Mianlüe oceanic basin opened in the Devonian; South Qinling was backarc shelf and interplatform basin-platform at the same time. (3)Triassic: continental collision orogeny, stage of foreland basins. (4) Jurassic-Cretaceous: stage of fault basins and depressional basins.
As the eastern part of the Central Orogenic Belt, Qinling-Dabie Orogenic Belt has a complicated tectonic-sedimentary history. On the basis of a systematic research on the lithostratigraphy, fossil assemblages, isotopic geochronology and tectonics of 4 secondary and 13 three-level tectonic units, this paper divides the study area into 18 types of sedimentary basins, and discusses its tectonic-sedimentary evolution from Neoproterozoic to Mesozoic: (1) Neoproterozoic-Early Paleozoic: North Qinling was magmatic arc and forearc basin; South Qinling experienced intracontinental rift to interplatform basin-platform to continental-margin rift; Dabie-Sulu experienced intracontinental rift to interplatform basin-platform. (2) Late Paleozoic: North Qinling was marine-continental alternation epeiric sea; Mianlüe oceanic basin opened in the Devonian; South Qinling was backarc shelf and interplatform basin-platform at the same time. (3)Triassic: continental collision orogeny, stage of foreland basins. (4) Jurassic-Cretaceous: stage of fault basins and depressional basins.
2014, 39(8): 1200-1216.
doi: 10.3799/dqkx.2014.104
Abstract:
Tarim basin, located in southern Xinjiang Uygur Autonomous Region of Northwest China, held among the Tianshan, Kunlun and Altun fold belts, is a large, superimposed basin which has a long evolutional history. Based on the comprehensive study of the previous results, we conduct a comparative study of lithostragraphy and sedimentary, and divide the Tarim area into 8 types of sedimentary basin during Neoproterozoic-Mesozoic, including passive continental margin, failed rift, carbonate platform, clastic epeiric sea, residual sea, mixed clastic-carbonate epeiric sea, inland graben basin, and foreland basin.The tectonic environments of basin formation and evolution are analyzed in this paper: Early Neoproterozoic, Tarim turned into stable stage of cover development.During Qingbaikouan, rift and passive continental margin were developed.Nanhua-Early Sinian, mortality rift and continental glaciers were developed.Carbonate platform, clastic epeiric sea and clastic-carbonate epeiric sea mainly developed during Paleozoic. The collision between Tarim and Kazakhstan-Junggar plate led to later subduction of the southern Tianshan oceanic basin of Carboniferous at the Late Carboniferous-Early Permian. At the beginning of Middle Permian, most of the Tarim evolved to foreland basin.
Tarim basin, located in southern Xinjiang Uygur Autonomous Region of Northwest China, held among the Tianshan, Kunlun and Altun fold belts, is a large, superimposed basin which has a long evolutional history. Based on the comprehensive study of the previous results, we conduct a comparative study of lithostragraphy and sedimentary, and divide the Tarim area into 8 types of sedimentary basin during Neoproterozoic-Mesozoic, including passive continental margin, failed rift, carbonate platform, clastic epeiric sea, residual sea, mixed clastic-carbonate epeiric sea, inland graben basin, and foreland basin.The tectonic environments of basin formation and evolution are analyzed in this paper: Early Neoproterozoic, Tarim turned into stable stage of cover development.During Qingbaikouan, rift and passive continental margin were developed.Nanhua-Early Sinian, mortality rift and continental glaciers were developed.Carbonate platform, clastic epeiric sea and clastic-carbonate epeiric sea mainly developed during Paleozoic. The collision between Tarim and Kazakhstan-Junggar plate led to later subduction of the southern Tianshan oceanic basin of Carboniferous at the Late Carboniferous-Early Permian. At the beginning of Middle Permian, most of the Tarim evolved to foreland basin.
2014, 39(8): 1217-1229.
doi: 10.3799/dqkx.2014.105
Abstract:
The structure and evolution of Qiangtang-Sanjiang during Paleozoic-Mesozoic sedimentary basins were controlled by the Tethys. On the basis of the exploration of previous studies on lithostratigraphy, fossil assemblages, isotopic geochronology and tectonics of the study area, this paper classifies the sedimentary basins of Qiangtang-Sanjiang region, and analyzes the formation and evolution of each sedimentary basin. During the Early Paleozoic, Qiangtang-Sanjiang basins were mostly ocean environment; with the subduction of the Tethys Ocean to the northeastward and southeastward in Late Paleozoic, the active margin sedimentary basins developed in this area, forming Jinshajiang back arc-ocean, Lancangjiang back arc-ocean and Ganzi-Litang back arc-ocean and then the multiple island arc-basin systems of eastern Tethys system gradually formed. During the Mesozoic, with the subduction of the Tethys in Late Triassic in Qiangtang-Sanjiang, three arc-basins gradually closed, then large-scale arc-arc collision and arc-continent collision occurred in this area. This area eventually entered intracontinental evolution stage from the active margin sedimentary basins, Due to the close of Tethys in Cretaceous, the Indian plate and western China collided, inland basins developed in Qiangtang-Sanjiang.
The structure and evolution of Qiangtang-Sanjiang during Paleozoic-Mesozoic sedimentary basins were controlled by the Tethys. On the basis of the exploration of previous studies on lithostratigraphy, fossil assemblages, isotopic geochronology and tectonics of the study area, this paper classifies the sedimentary basins of Qiangtang-Sanjiang region, and analyzes the formation and evolution of each sedimentary basin. During the Early Paleozoic, Qiangtang-Sanjiang basins were mostly ocean environment; with the subduction of the Tethys Ocean to the northeastward and southeastward in Late Paleozoic, the active margin sedimentary basins developed in this area, forming Jinshajiang back arc-ocean, Lancangjiang back arc-ocean and Ganzi-Litang back arc-ocean and then the multiple island arc-basin systems of eastern Tethys system gradually formed. During the Mesozoic, with the subduction of the Tethys in Late Triassic in Qiangtang-Sanjiang, three arc-basins gradually closed, then large-scale arc-arc collision and arc-continent collision occurred in this area. This area eventually entered intracontinental evolution stage from the active margin sedimentary basins, Due to the close of Tethys in Cretaceous, the Indian plate and western China collided, inland basins developed in Qiangtang-Sanjiang.
2014, 39(8): 1230-1242.
doi: 10.3799/dqkx.2014.106
Abstract:
On the basis of divisions of tectonic-stratum of the North China block (NCB) area, this article discusses the type of sedimentary basins formation region, filling sequence and temporal evolution of different tectonic-stratum zones for each construction phase according to five tectonic stages as Mesoproterozoic-Neoproterozoic, Paleozoic, Late Paleozoic, Triassic-Early Jurassic, Middle Jurassic-Cretaceous. Meso-Neoproterozoic is the stage of development of periphery rifting. Cambrian-Early, Middle Ordovician, North China plate synchronized global settlement and received extensive transgression, forming widespread carbonate platform of almost all north China. Late Ordovician-Devonian, NCB overall uplift and erosion, sedimentation is missing. Carboniferous-Permian, North China block subsided again and suffered transgression, forming a broad epicontinental sea paralic deposition. To Late Permian, NCB entered the stage of continental basin development. Mesozoic, continental tectonic activities were active, forming fault basins, sag basins and pull-apart basins broadly.
On the basis of divisions of tectonic-stratum of the North China block (NCB) area, this article discusses the type of sedimentary basins formation region, filling sequence and temporal evolution of different tectonic-stratum zones for each construction phase according to five tectonic stages as Mesoproterozoic-Neoproterozoic, Paleozoic, Late Paleozoic, Triassic-Early Jurassic, Middle Jurassic-Cretaceous. Meso-Neoproterozoic is the stage of development of periphery rifting. Cambrian-Early, Middle Ordovician, North China plate synchronized global settlement and received extensive transgression, forming widespread carbonate platform of almost all north China. Late Ordovician-Devonian, NCB overall uplift and erosion, sedimentation is missing. Carboniferous-Permian, North China block subsided again and suffered transgression, forming a broad epicontinental sea paralic deposition. To Late Permian, NCB entered the stage of continental basin development. Mesozoic, continental tectonic activities were active, forming fault basins, sag basins and pull-apart basins broadly.
2014, 39(8): 1035-1051.
doi: 10.3799/dqkx.2014.093
Abstract:
During the Cenozoic, strong multi-stage tectonic events occurred in western China, which experienced a complex tectonic-geomorphic evolution history. Tectonic setting and geodynamic process determined the tectonic-geomorphic evolutions in the continent of western China. Sedimentary basin-orogen belt systems are the dominant basic structural pattern in western China during the Cenozoic. Basin-range pattern is the major geomorphic unit in western China. According to the geometric, dynamic features of tectonic evolution of basins, the Cenozoic sedimentary basins in western China fall into four tectonic categories: contractional basin, faulted basin, strike-slip pull-apart basin and remnant sea-foreland basin. These closed geomorphic basins in western China were surrounded by orogenic belts, which are divided by active compressive faults (thrust fault and strike-slip fault). Both the Indian-Eurasian plate collision and the intracontinental subduction play significant role in the formation and evolution of sedimentary basins in western China. There is a close relationship among the tectonic lithofacies paleogeographic evolution of sedimentary basins, plate movement and tectonic uplift.
During the Cenozoic, strong multi-stage tectonic events occurred in western China, which experienced a complex tectonic-geomorphic evolution history. Tectonic setting and geodynamic process determined the tectonic-geomorphic evolutions in the continent of western China. Sedimentary basin-orogen belt systems are the dominant basic structural pattern in western China during the Cenozoic. Basin-range pattern is the major geomorphic unit in western China. According to the geometric, dynamic features of tectonic evolution of basins, the Cenozoic sedimentary basins in western China fall into four tectonic categories: contractional basin, faulted basin, strike-slip pull-apart basin and remnant sea-foreland basin. These closed geomorphic basins in western China were surrounded by orogenic belts, which are divided by active compressive faults (thrust fault and strike-slip fault). Both the Indian-Eurasian plate collision and the intracontinental subduction play significant role in the formation and evolution of sedimentary basins in western China. There is a close relationship among the tectonic lithofacies paleogeographic evolution of sedimentary basins, plate movement and tectonic uplift.
2014, 39(8): 1052-1064.
doi: 10.3799/dqkx.2014.094
Abstract:
The Gangdese area is located in the middle of the Tibetan Plateau. Its southern boundary is the Indus River-Brahmaputra suture zone, and northern boundary is the Bangonghu-Shuanghu-Nujiang suture zone. It is a huge tectonic-magmatic belt, nearly east-west directed. The Gangdese is divided into eight tectonic-stratigraphic subregions in this paper. The sedimentary features of eight stratigraphic subregions in different periods are generalized from Neoproterozoic to Mesozoic, and the development and evolution of the sedimentary basins in Gangdese, Tibet plateau is explored. The following three stages of evolution are revealed: (1) the Gangdese started the evolution of continental-margin rift from Sinian; (2) it mainly developed carbonate sedimentary basins in the Late Paleozoic, featuring stable and broad development of carbonate platform and interplatform basins in this period. Gangdese started the development of rifted continental margin of stretch properties from Carboniferous, and the main sedimentary basins became continental-margin rift; (3) it was denuded in most areas from Early Mesozoic due to continental uplift. As Bangonghu-Nujiang Tethys's subduction towards north and Brahmaputra's subduction towards south, the Gangdese developed large magmatic arc belt at last in Late Mesozoic, and the main sedimentary basins changed to retroarc basin, interarc basin and forearc basin.
The Gangdese area is located in the middle of the Tibetan Plateau. Its southern boundary is the Indus River-Brahmaputra suture zone, and northern boundary is the Bangonghu-Shuanghu-Nujiang suture zone. It is a huge tectonic-magmatic belt, nearly east-west directed. The Gangdese is divided into eight tectonic-stratigraphic subregions in this paper. The sedimentary features of eight stratigraphic subregions in different periods are generalized from Neoproterozoic to Mesozoic, and the development and evolution of the sedimentary basins in Gangdese, Tibet plateau is explored. The following three stages of evolution are revealed: (1) the Gangdese started the evolution of continental-margin rift from Sinian; (2) it mainly developed carbonate sedimentary basins in the Late Paleozoic, featuring stable and broad development of carbonate platform and interplatform basins in this period. Gangdese started the development of rifted continental margin of stretch properties from Carboniferous, and the main sedimentary basins became continental-margin rift; (3) it was denuded in most areas from Early Mesozoic due to continental uplift. As Bangonghu-Nujiang Tethys's subduction towards north and Brahmaputra's subduction towards south, the Gangdese developed large magmatic arc belt at last in Late Mesozoic, and the main sedimentary basins changed to retroarc basin, interarc basin and forearc basin.
2014, 39(8): 1065-1078.
doi: 10.3799/dqkx.2014.095
Abstract:
The geotectonic environments are reconstructed and presented in this paper. Firstly, the Mesozoic sedimentary formation of the Upper Yangtze is studied in detail, then the basin features are analyzed based on the lithology of each unit (formation) and the space distribution framework of basins is established. Eventually, three stages of tectonic evolution of the Upper Yangtze are summarized by means of detailed analysis of chronostratigraphic and biostratigraphic correlations, paleogeography of biology, lithofacies and tectonics. The Upper Yangtze region rose continuously, water of which became shallow, and a series of clastic-carbonate epeiric sea and platform-interplatform basin sedimentary basin formed because of Indosinian orogeny during Early-Middle Triassic. When it came to Late Triassic to Early Jurassic, the Upper Yangtze collided with the Tethys domain block or arc-basin collisional zone in its west, the paleogeographic environments in the southwest and north of which turned to foreland basin and peripheral foreland basin, while the Xuefeng uplift turned orogeny. After middle Jurassic, with the subduction of paleo-Pacific plate to Asia plate, the south Upper Yangtze came into continental orogenic stage that mainly developed a series of downwarped basins to the east of Xuefeng Mountain and a large-scale depressional basin to the west.
The geotectonic environments are reconstructed and presented in this paper. Firstly, the Mesozoic sedimentary formation of the Upper Yangtze is studied in detail, then the basin features are analyzed based on the lithology of each unit (formation) and the space distribution framework of basins is established. Eventually, three stages of tectonic evolution of the Upper Yangtze are summarized by means of detailed analysis of chronostratigraphic and biostratigraphic correlations, paleogeography of biology, lithofacies and tectonics. The Upper Yangtze region rose continuously, water of which became shallow, and a series of clastic-carbonate epeiric sea and platform-interplatform basin sedimentary basin formed because of Indosinian orogeny during Early-Middle Triassic. When it came to Late Triassic to Early Jurassic, the Upper Yangtze collided with the Tethys domain block or arc-basin collisional zone in its west, the paleogeographic environments in the southwest and north of which turned to foreland basin and peripheral foreland basin, while the Xuefeng uplift turned orogeny. After middle Jurassic, with the subduction of paleo-Pacific plate to Asia plate, the south Upper Yangtze came into continental orogenic stage that mainly developed a series of downwarped basins to the east of Xuefeng Mountain and a large-scale depressional basin to the west.
2014, 39(8): 1079-1098.
doi: 10.3799/dqkx.2014.096
Abstract:
With subduction collision between Eurasian plate and surrounding plates such as Indian, Australian, Philippine and Pacific plates, a series of marginal sea basins, and faulted-downwarped basins formed in the continental margin of eastern China, mainly including Songliao, Bohai Bay, Jianghan, Subei, East China Sea, Pearl River Mouth and Beibuwan basins. Based on Mesozoic tectonic background analysis and Cenozoic distribution characteristics of sedimentary basins in eastern China, sedimentary sequence and tectonic evolution of 7 main basins are analyzed in detail.through a comparative study of tectonic evolution of the surrounding plates and the Tan-Lu fault, volcanism, low temperature thermochronology, climatic evolvement, and so on.It is found that the tectonic evolution of the sedimentary basins in eastern China can be divided into three phases, which are Paleocene-Eocene, Oligocene-Early Miocene and Late Miocene-Quaternary respectively.
With subduction collision between Eurasian plate and surrounding plates such as Indian, Australian, Philippine and Pacific plates, a series of marginal sea basins, and faulted-downwarped basins formed in the continental margin of eastern China, mainly including Songliao, Bohai Bay, Jianghan, Subei, East China Sea, Pearl River Mouth and Beibuwan basins. Based on Mesozoic tectonic background analysis and Cenozoic distribution characteristics of sedimentary basins in eastern China, sedimentary sequence and tectonic evolution of 7 main basins are analyzed in detail.through a comparative study of tectonic evolution of the surrounding plates and the Tan-Lu fault, volcanism, low temperature thermochronology, climatic evolvement, and so on.It is found that the tectonic evolution of the sedimentary basins in eastern China can be divided into three phases, which are Paleocene-Eocene, Oligocene-Early Miocene and Late Miocene-Quaternary respectively.
2014, 39(8): 1099-1118.
doi: 10.3799/dqkx.2014.097
Abstract:
The Ertix-Xar Moron suture is located at the joint part of Siberia, North China and Junggar, and its tectonic evolution has a close relationship with the opening and closing of Paleo-Asian Ocean basin.In this paper, plates the sedimentary basin types are reconstruted and define 10 basin types by an integrated research on the Paleozoic lithostratigraphy, biostratigraphy and chronostratigraphy are defined. The structure-sedimentary evolution of the study area is discussed based on the sedimentary basin-fill sequence and concluded as the following stages: (1) Early Paleozoic-Early Carboniferous subduction stage of the Paleo-Asian Ocean; (2) Early, Late Carboniferous collisional stage; (3) Late Carboniferous-Early Permian collision and post-collisional evolution stage. It is suggested that the Paleo-Asian Ocean closed from west to east like "scissors", and the closing began from the end of the Early Carboniferous (318 Ma) to the Middle Permian-Early Triassic (260-245 Ma).During Triassic, the Paleo-Asian Ocean disappeared and converted to total terrestrial environment.
The Ertix-Xar Moron suture is located at the joint part of Siberia, North China and Junggar, and its tectonic evolution has a close relationship with the opening and closing of Paleo-Asian Ocean basin.In this paper, plates the sedimentary basin types are reconstruted and define 10 basin types by an integrated research on the Paleozoic lithostratigraphy, biostratigraphy and chronostratigraphy are defined. The structure-sedimentary evolution of the study area is discussed based on the sedimentary basin-fill sequence and concluded as the following stages: (1) Early Paleozoic-Early Carboniferous subduction stage of the Paleo-Asian Ocean; (2) Early, Late Carboniferous collisional stage; (3) Late Carboniferous-Early Permian collision and post-collisional evolution stage. It is suggested that the Paleo-Asian Ocean closed from west to east like "scissors", and the closing began from the end of the Early Carboniferous (318 Ma) to the Middle Permian-Early Triassic (260-245 Ma).During Triassic, the Paleo-Asian Ocean disappeared and converted to total terrestrial environment.
2014, 39(8): 1119-1128.
doi: 10.3799/dqkx.2014.098
Abstract:
The South Tianshan is an orogenic belt formed due to the collision of the Tarim plate and Ili-Kazakhstan plate. Previous researches indicate that the South Tianshan evolved from expansion into subduction, and eventually into collision orogenesis in Paleozoic and it entered intracontinental development stage in Mesozoic. Debates about the time of collision and the evolution stages persist because of its special geographic location and complicated tectonic setting. In this paper, some stratigraphic subregions are determined according to geological records and sedimentary analysis. The evolution of these Paleozoic-Mesozoic sedimentary sequences is divided into the following five stages. As a back-arc basin, it developed from small oceanic basin to mature oceanic basin from Cambrian to Ordovician. The South Tianshan Ocean started subducting. Hongliuhe started closing in Early Silurian, with the eastern part of South Tianshan ocean completely closed in Early Devonian, while the southwest Tianshan continued subducting until the end of Devonian. During Carboniferous and Early Permian, residual basin still existed in the west. It disappeared in Permian and the west of the South Tianshan finally crashed to orogenic belt. In Mesozoic, it developed to intracontinental stage. The whole region has been denuded during Triassic. The western part became fault basins in Jurassic and continued in Cretaceous. The eastern part has been denuded during Jurassic and it developed into pull-apart basins in Cretaceous.
The South Tianshan is an orogenic belt formed due to the collision of the Tarim plate and Ili-Kazakhstan plate. Previous researches indicate that the South Tianshan evolved from expansion into subduction, and eventually into collision orogenesis in Paleozoic and it entered intracontinental development stage in Mesozoic. Debates about the time of collision and the evolution stages persist because of its special geographic location and complicated tectonic setting. In this paper, some stratigraphic subregions are determined according to geological records and sedimentary analysis. The evolution of these Paleozoic-Mesozoic sedimentary sequences is divided into the following five stages. As a back-arc basin, it developed from small oceanic basin to mature oceanic basin from Cambrian to Ordovician. The South Tianshan Ocean started subducting. Hongliuhe started closing in Early Silurian, with the eastern part of South Tianshan ocean completely closed in Early Devonian, while the southwest Tianshan continued subducting until the end of Devonian. During Carboniferous and Early Permian, residual basin still existed in the west. It disappeared in Permian and the west of the South Tianshan finally crashed to orogenic belt. In Mesozoic, it developed to intracontinental stage. The whole region has been denuded during Triassic. The western part became fault basins in Jurassic and continued in Cretaceous. The eastern part has been denuded during Jurassic and it developed into pull-apart basins in Cretaceous.
2014, 39(8): 1129-1139.
doi: 10.3799/dqkx.2014.099
Abstract:
On the western margin of the Baoshan block, a set of tectonic mélange can be seen along the western Lushui-Luxi tectonic zone. It is characterized by matrices consisting of strongly deformed and low-grade metamorphic clastic rocks bearing graptolite of Sinian-Paleozoic Pumanshao Group and Gongyanghe Group and volcanic flysch turbidite, and structural lens consisting of siliceous, graywacke, part limestone, conglomerate, basalt and granite. The ages of these rocks range from Sinian to Paleozoic and get younger from east to west, which shows the characters of retrogressive accretion. In the early stage, the structural styles are characterized by imbricate structures formed by thrust faults and homoclinal-overturned folds, and nearly N-S-trending shear in the late stage. The characteristics of basalt-andesite and rhylite are of arc volcanic rocks, and the basalt shows characteristics of continental intraplate volcanic rocks. Both of the two types of volcanic rocks maybe account for the tectonic setting of island arc and back-arc extension. Cambrian and Ordovician granite can be divided into the western belt and eastern belt, and the ages of the latter are earlier than that of the former. Those granites are part of magmatic arc of the western margin of the Baoshan block. Therefore, this tectonic mélange records the geological events such as extinction to the subduction of the oceanic crust and magmatic sedimentation-volcanic-magmatic-tectonic events during the formation process of accretionary wedge, and also records the information of the Early Paleozoic accretionary orogenesis on the western margin of the Baoshan block. Meanwhile, it suggests the existence of an ocean basin during Sinian-Paleozoic in the Lushui-Luxi tectonic zone.
On the western margin of the Baoshan block, a set of tectonic mélange can be seen along the western Lushui-Luxi tectonic zone. It is characterized by matrices consisting of strongly deformed and low-grade metamorphic clastic rocks bearing graptolite of Sinian-Paleozoic Pumanshao Group and Gongyanghe Group and volcanic flysch turbidite, and structural lens consisting of siliceous, graywacke, part limestone, conglomerate, basalt and granite. The ages of these rocks range from Sinian to Paleozoic and get younger from east to west, which shows the characters of retrogressive accretion. In the early stage, the structural styles are characterized by imbricate structures formed by thrust faults and homoclinal-overturned folds, and nearly N-S-trending shear in the late stage. The characteristics of basalt-andesite and rhylite are of arc volcanic rocks, and the basalt shows characteristics of continental intraplate volcanic rocks. Both of the two types of volcanic rocks maybe account for the tectonic setting of island arc and back-arc extension. Cambrian and Ordovician granite can be divided into the western belt and eastern belt, and the ages of the latter are earlier than that of the former. Those granites are part of magmatic arc of the western margin of the Baoshan block. Therefore, this tectonic mélange records the geological events such as extinction to the subduction of the oceanic crust and magmatic sedimentation-volcanic-magmatic-tectonic events during the formation process of accretionary wedge, and also records the information of the Early Paleozoic accretionary orogenesis on the western margin of the Baoshan block. Meanwhile, it suggests the existence of an ocean basin during Sinian-Paleozoic in the Lushui-Luxi tectonic zone.
