The Laji Shan—Jishi Shan tectonic belt(LJTB),located in the southern part of the northeastern Tibetan Plateau(NETP),is a tectonic window to reveal regional tectonic deformation in the NETP.However,its kinematics in t...The Laji Shan—Jishi Shan tectonic belt(LJTB),located in the southern part of the northeastern Tibetan Plateau(NETP),is a tectonic window to reveal regional tectonic deformation in the NETP.However,its kinematics in the Holocene remains controversial.We obtain the latest and dense horizontal velocity field based on data collected from our newly constructed and existing GNSS stations.Combined with fault kinematics from geologic observations,we analyze the crustal deformation characteristics along the LJTB.The results show that:(1)The Laji Shan fault(LJF)is inactive,and the northwest-oriented Jishi Shan fault(JSF)exhibits a significant dextral and thrust slip.(2)The transpression along the arc-shaped LJTB accommodates deformation transformation between the dextral Riyue Shan fault and the sinistral west Qinling fault.(3)With the continuous pushing of the Indian plate,internal strains in the Tibetan Plateau are continuously transferred in the northeast via the LJTB as they are gradually dissipated near the LJTB and translated into significant crustal uplift in these regions.展开更多
The Lajishan orogenic belt is one of the E-W-trending Caledonian orogenicbelts within the Qinling-Qilian orogenic system. It was formed upon the Jiningian basement byintensive taphrogenesis. Its major characteristics ...The Lajishan orogenic belt is one of the E-W-trending Caledonian orogenicbelts within the Qinling-Qilian orogenic system. It was formed upon the Jiningian basement byintensive taphrogenesis. Its major characteristics comprise the prominent faulting along the northand south boundaries, the highly complicated petrological and petro-geochemical features of thevolcanic rock series, and the development of a new type of ophiolite suite. In terms of tectonicanalysis and the sequential analysis of tectonic settings of magmatic rocks, it is suggested thatthe Lajishan orogenic belt has undergone a complete 'opening-closing' cycle, which can be furtherdivided into 3 second-order 'opening-closing' cycles. The composite characteristics of the'opening-closing' movement show that Laji Mountain is a typical fault orogenic belt. The faultorogenic belt is one of the most important types of intracontinental orogens. It is of criticaltheoretical and practical significance to summarize the characteristics and the diagnostic criteriaof this kind of orogenic belts, and study the mechanism of their formation and build models of theirevolution.展开更多
Laji Shan is located in the eastern part of Qinghai Province,sandwiched between Xining and Hualong Basins.It is about 250km long and 10～20km wide from Riyueshan in the west to Minheguanting in the east.Laji Shan belo...Laji Shan is located in the eastern part of Qinghai Province,sandwiched between Xining and Hualong Basins.It is about 250km long and 10～20km wide from Riyueshan in the west to Minheguanting in the east.Laji Shan belongs to the Caledonian orogenic belt.Its basement consists of the rocks of Palaeo\|Protero zoic Hualong Group (Pt 1 hl ) and Neo\|Proterozoic Huangzhong Group (Pt\-3 h ).There are ptygmatic folds,closely linear type folds,strongly structural d ifferentiation and schistosity developed,suggesting that the basement underwent deep seated ductile deformation.The main part of Laji Shan is composed of Early\|Palaeozoic marine facies volcanic rocks and clastic sedimentary rocks,and suffered greenschist facies metamorphism and brittle\|ductile deformation.Others are composed of Ea rly\|Palaeozoic basic and ultrabasic rocks,intermediate\|acidic intruded rocks a nd dike rocks.Devonian molasse formation in Laji Shan is in uncomfortable contac t with underlying strata.Jurassic and Cretaceous systems are intermont basin dep osits,corresponding to a cover.展开更多
This paper deals with the anisotropy of magnetic susceptibility (AMS) of Laji Shan and its adjacent areas. Cenozoic sediment is a suite of mudstone and sandstone, which underwent weak deformation and no metamorphism. ...This paper deals with the anisotropy of magnetic susceptibility (AMS) of Laji Shan and its adjacent areas. Cenozoic sediment is a suite of mudstone and sandstone, which underwent weak deformation and no metamorphism. Most of the magnetic ellipsoids are oblate with K_max trending NW-SE, and the minimum axes K_min show a large deviation from the poles of bedding planes with an NE preferred direction. Taken together, they reflect that the magnetic fabric is mainly of tectonic origin. In the study area, the NE-SW orientation of K_min represents the recent principal compression direction. This point is substantiated by the structures in sites where magnetic fabric data are also available. The stress field provides a strong support for the sustained uplift of Laji Shan and its adjacent areas in the late Tertiary-Quaternary period.展开更多
基金supported by the National Science Foundation of China(41874117)the Second Tibetan Plateau Scientific Expedition and Research Program(SETP)(2019QZKK0901)Natural Science Basic Research Program of Shaanxi(Program No.2023-JC-ON-0309)。
文摘The Laji Shan—Jishi Shan tectonic belt(LJTB),located in the southern part of the northeastern Tibetan Plateau(NETP),is a tectonic window to reveal regional tectonic deformation in the NETP.However,its kinematics in the Holocene remains controversial.We obtain the latest and dense horizontal velocity field based on data collected from our newly constructed and existing GNSS stations.Combined with fault kinematics from geologic observations,we analyze the crustal deformation characteristics along the LJTB.The results show that:(1)The Laji Shan fault(LJF)is inactive,and the northwest-oriented Jishi Shan fault(JSF)exhibits a significant dextral and thrust slip.(2)The transpression along the arc-shaped LJTB accommodates deformation transformation between the dextral Riyue Shan fault and the sinistral west Qinling fault.(3)With the continuous pushing of the Indian plate,internal strains in the Tibetan Plateau are continuously transferred in the northeast via the LJTB as they are gradually dissipated near the LJTB and translated into significant crustal uplift in these regions.
基金the Doctoral Programme of Higher Education 97049119 the National Natural Science Foundation of China grant 40072062.
文摘The Lajishan orogenic belt is one of the E-W-trending Caledonian orogenicbelts within the Qinling-Qilian orogenic system. It was formed upon the Jiningian basement byintensive taphrogenesis. Its major characteristics comprise the prominent faulting along the northand south boundaries, the highly complicated petrological and petro-geochemical features of thevolcanic rock series, and the development of a new type of ophiolite suite. In terms of tectonicanalysis and the sequential analysis of tectonic settings of magmatic rocks, it is suggested thatthe Lajishan orogenic belt has undergone a complete 'opening-closing' cycle, which can be furtherdivided into 3 second-order 'opening-closing' cycles. The composite characteristics of the'opening-closing' movement show that Laji Mountain is a typical fault orogenic belt. The faultorogenic belt is one of the most important types of intracontinental orogens. It is of criticaltheoretical and practical significance to summarize the characteristics and the diagnostic criteriaof this kind of orogenic belts, and study the mechanism of their formation and build models of theirevolution.
文摘Laji Shan is located in the eastern part of Qinghai Province,sandwiched between Xining and Hualong Basins.It is about 250km long and 10～20km wide from Riyueshan in the west to Minheguanting in the east.Laji Shan belongs to the Caledonian orogenic belt.Its basement consists of the rocks of Palaeo\|Protero zoic Hualong Group (Pt 1 hl ) and Neo\|Proterozoic Huangzhong Group (Pt\-3 h ).There are ptygmatic folds,closely linear type folds,strongly structural d ifferentiation and schistosity developed,suggesting that the basement underwent deep seated ductile deformation.The main part of Laji Shan is composed of Early\|Palaeozoic marine facies volcanic rocks and clastic sedimentary rocks,and suffered greenschist facies metamorphism and brittle\|ductile deformation.Others are composed of Ea rly\|Palaeozoic basic and ultrabasic rocks,intermediate\|acidic intruded rocks a nd dike rocks.Devonian molasse formation in Laji Shan is in uncomfortable contac t with underlying strata.Jurassic and Cretaceous systems are intermont basin dep osits,corresponding to a cover.
基金the National (Grant No. G1998040800) and CAS's Key Project forBasic Research on Tibetan Plateau (Grant Nos. KZ951-A1-204 and KZ95T-06), and the National Natural Science Foundation of China (Grant No. 49902019).
文摘This paper deals with the anisotropy of magnetic susceptibility (AMS) of Laji Shan and its adjacent areas. Cenozoic sediment is a suite of mudstone and sandstone, which underwent weak deformation and no metamorphism. Most of the magnetic ellipsoids are oblate with K_max trending NW-SE, and the minimum axes K_min show a large deviation from the poles of bedding planes with an NE preferred direction. Taken together, they reflect that the magnetic fabric is mainly of tectonic origin. In the study area, the NE-SW orientation of K_min represents the recent principal compression direction. This point is substantiated by the structures in sites where magnetic fabric data are also available. The stress field provides a strong support for the sustained uplift of Laji Shan and its adjacent areas in the late Tertiary-Quaternary period.
