The North Qilian Shan fold and thrust belt,located at the northern Tibetan Plateau and southern margin of the Hexi Corridor,is a key tectonic unit to decode the formation and expansion of the plateau.Previous studies ...The North Qilian Shan fold and thrust belt,located at the northern Tibetan Plateau and southern margin of the Hexi Corridor,is a key tectonic unit to decode the formation and expansion of the plateau.Previous studies emphasize the Cenozoic deformation due to the far-field response to the Indo-Asian collision,but the Mesozoic deformations are poorly constrained in this area.We conducted detailed field mapping,structural analysis,geochronology,and structural interpretation of deep seismic reflectional profiling and magnetotelluric(MT)sounding,to address the superposed results of the Mesozoic and Cenozoic deformation.The results recognized the North Qilian thrust and nappe system(NQTS),the root and the frontal belt are the North Qilian thrust(NQT),and the Yumu Shan klippe(YK),respectively.The middle belt is located between the NQT and the YK.Monzonitic granite zircon U-Pb dating from the middle belt yields an age of ca.415 Ma,which is similar to south NQT.The thrusting displacement is estimated at ca.48 km by structural interpretation of deep profiles.The timing is constrained in the early stage of the Early Cretaceous by the formation of simultaneous growth strata.We suggest that the NQTS has resulted from the far-field effect of the Lhasa-Qiangtang collision,and the Yumu Shan is uplifted by the superposed Cenozoic deformation.展开更多
Since the Quaternary, many lakes have been present in the Qinghai-Tibetan Plateau. As peculiar geological processes in the evolution of the uplifting of Qinghai-Tibetan Plateau, the distributions and evolutions of the...Since the Quaternary, many lakes have been present in the Qinghai-Tibetan Plateau. As peculiar geological processes in the evolution of the uplifting of Qinghai-Tibetan Plateau, the distributions and evolutions of the Quaternary paleolakes in the Qinghai-Tibetan Plateau have been the focus of interest among the international geosciences circle. Comparisons of the newly obtained and existing data from field surveys, remote sensing images, characteristics of tectonic landforms and distribution of the lacustrine strata, the author have, for the first time, defined a large-sized Quaternary Qiangtang Paleolake. The paleolake starts from the east-westerly direction at Rutog in western Tibet, passing through Gerze, and finally ends at Nagqu in eastern Tibet. Its length is approximately 1,200 kin; it is about 420 km at its widest point （north-southerly）. The Paleolake forms an E-W （or NWW） ellipsoid with an estimated area of 354920 km2. The Paleolake is bordered by the Mts. Gangdise and Nyainqentanglha to the south and the Karakorum Pass-Toze Kangri-Zangbagangri- Tanggula Pass to the north. It generally appears as a basinal landform with low mountains and valleys in the central part （altitudes of 4400 m） and higher altitudes （5000 m） in the peripheries. The formation and development of the Paleolake was controlled by the nearly E-W trending structures. There are three east-westerly extending tectonic sutures inside the Paleolake area, from north to south： （1） the Shuanghu Suture; （2） the Bangong Co-Nujiang River Suture; （3） the Shiquanhe-Lhari Suture. These three sutures have generally controlled the spreading features of the Paleolake and act as the first grade lake-controlling structures. In the southern Paleolake basin, there are a series of south-northerly rift basins, which are controlled by the normal faults and exist as a series of south-northerly grabens and semi-graben faulted basins. The south- northerly rift zones have clearly exerted control over the south margin of the Paleolake as well as the distribution of the residual lake basins after the Paleolake＇s break up. They are the secondary lake- controlling tectonics. Discoveries of the lacustrine strata inside the Plateau, especially the successive discoveries of many high-stand lacustrine strata, are direct evidence supporting the existence of the paleolakes in the Plateau. The dating results of the lake-eroded travertine in the Dong Co in the hinterland of the Quaternary Qiangtang Paleolake have revealed that the lake-eroded travertine is of Late Pleistocene sediments. By considering the analysis of the lacustrine strata as well, the researchers have revealed that the Quaternary Qiangtang Paleolake begins its embryonic form in the Early Pleistocene, successively develops till the Middle Pleistocene, and reaches its full blossom in the middle stage of the Late Pleistocene; it further shrinks and separates by the end of the Late Pleistocene, and finally ceases its whole life as the paleolake. After the Holocene, the huge Late Pleistocene Qiangtang Paleolake no longer exists, leaving a series of widely distributed smaller lakes on the Qiangtang Plateau. These smaller, isolated water systems receive the Holocene lacustrine sediments.展开更多
基金financially supported by the China Geological Survey(Grant Nos.DD20230229,DD20160083,DD20190011,DD20221643-5)the National Key Research and Development Program of China(the DREAM—Deep Resource Exploration and Advanced Mining+1 种基金Grant No.2018YFC0603701)the Cooperative Project between the Chinese Academy of Geological Sciences and the Sinopec Shengli Oilfield Company(Grant No.P22065)。
文摘The North Qilian Shan fold and thrust belt,located at the northern Tibetan Plateau and southern margin of the Hexi Corridor,is a key tectonic unit to decode the formation and expansion of the plateau.Previous studies emphasize the Cenozoic deformation due to the far-field response to the Indo-Asian collision,but the Mesozoic deformations are poorly constrained in this area.We conducted detailed field mapping,structural analysis,geochronology,and structural interpretation of deep seismic reflectional profiling and magnetotelluric(MT)sounding,to address the superposed results of the Mesozoic and Cenozoic deformation.The results recognized the North Qilian thrust and nappe system(NQTS),the root and the frontal belt are the North Qilian thrust(NQT),and the Yumu Shan klippe(YK),respectively.The middle belt is located between the NQT and the YK.Monzonitic granite zircon U-Pb dating from the middle belt yields an age of ca.415 Ma,which is similar to south NQT.The thrusting displacement is estimated at ca.48 km by structural interpretation of deep profiles.The timing is constrained in the early stage of the Early Cretaceous by the formation of simultaneous growth strata.We suggest that the NQTS has resulted from the far-field effect of the Lhasa-Qiangtang collision,and the Yumu Shan is uplifted by the superposed Cenozoic deformation.
基金financially supported by the projects:"Neotectonics and Late Cenozoic Paleo Lakes in the Qinghai-Tibetan Plateau" (No. 1212010610108) and "Research on Paleo Lakes Climate Variation Records in Qinghai-Tibetan Plateau" (No. 1212011087114),which are both managed by the China Geological Survey and Project of Ministry of Science and Technology:"Scientific drilling in Wenchuan earthquake fault zone"
文摘Since the Quaternary, many lakes have been present in the Qinghai-Tibetan Plateau. As peculiar geological processes in the evolution of the uplifting of Qinghai-Tibetan Plateau, the distributions and evolutions of the Quaternary paleolakes in the Qinghai-Tibetan Plateau have been the focus of interest among the international geosciences circle. Comparisons of the newly obtained and existing data from field surveys, remote sensing images, characteristics of tectonic landforms and distribution of the lacustrine strata, the author have, for the first time, defined a large-sized Quaternary Qiangtang Paleolake. The paleolake starts from the east-westerly direction at Rutog in western Tibet, passing through Gerze, and finally ends at Nagqu in eastern Tibet. Its length is approximately 1,200 kin; it is about 420 km at its widest point （north-southerly）. The Paleolake forms an E-W （or NWW） ellipsoid with an estimated area of 354920 km2. The Paleolake is bordered by the Mts. Gangdise and Nyainqentanglha to the south and the Karakorum Pass-Toze Kangri-Zangbagangri- Tanggula Pass to the north. It generally appears as a basinal landform with low mountains and valleys in the central part （altitudes of 4400 m） and higher altitudes （5000 m） in the peripheries. The formation and development of the Paleolake was controlled by the nearly E-W trending structures. There are three east-westerly extending tectonic sutures inside the Paleolake area, from north to south： （1） the Shuanghu Suture; （2） the Bangong Co-Nujiang River Suture; （3） the Shiquanhe-Lhari Suture. These three sutures have generally controlled the spreading features of the Paleolake and act as the first grade lake-controlling structures. In the southern Paleolake basin, there are a series of south-northerly rift basins, which are controlled by the normal faults and exist as a series of south-northerly grabens and semi-graben faulted basins. The south- northerly rift zones have clearly exerted control over the south margin of the Paleolake as well as the distribution of the residual lake basins after the Paleolake＇s break up. They are the secondary lake- controlling tectonics. Discoveries of the lacustrine strata inside the Plateau, especially the successive discoveries of many high-stand lacustrine strata, are direct evidence supporting the existence of the paleolakes in the Plateau. The dating results of the lake-eroded travertine in the Dong Co in the hinterland of the Quaternary Qiangtang Paleolake have revealed that the lake-eroded travertine is of Late Pleistocene sediments. By considering the analysis of the lacustrine strata as well, the researchers have revealed that the Quaternary Qiangtang Paleolake begins its embryonic form in the Early Pleistocene, successively develops till the Middle Pleistocene, and reaches its full blossom in the middle stage of the Late Pleistocene; it further shrinks and separates by the end of the Late Pleistocene, and finally ceases its whole life as the paleolake. After the Holocene, the huge Late Pleistocene Qiangtang Paleolake no longer exists, leaving a series of widely distributed smaller lakes on the Qiangtang Plateau. These smaller, isolated water systems receive the Holocene lacustrine sediments.
