We have studied the evolution of the tectonic lithofacies paleogeography of Paleocene- Eocene, Oligocene, Miocene, and Pliocene of the Qinghai-Tibet Plateau by compiling data regarding the type, tectonic setting, and ...We have studied the evolution of the tectonic lithofacies paleogeography of Paleocene- Eocene, Oligocene, Miocene, and Pliocene of the Qinghai-Tibet Plateau by compiling data regarding the type, tectonic setting, and iithostratigraphic sequence of 98 remnant basins in the plateau area. Our results can be summarized as follows. （1） The Paleocene to Eocene is characterized by uplift and erosion in the Songpan-Garze and Gangdise belts, depression （lakes and pluvial plains） in eastern Tarim, Qaidam, Qiangtang, and Hoh Xil, and the Neo-Tethys Sea in the western and southern Qinghai-Tibet Plateau. （2） The Oligocene is characterized by uplift in the Gangdise--Himalaya and Karakorum regions （marked by the absence of sedimentation）, fluvial transport （originating eastward and flowing westward） in the Brahmaputra region （marked by the deposition of Dazhuka conglomerate）, uplift and erosion in western Kunlun and Songpan-Garze, and depression （lakes） in the Tarim, Qaidam, Qiangtang, and Hoh Xil. The Oligocene is further characterized by depressional littoral and neritic basins in southwestern Tarim, with marine facies deposition ceasing at the end of the Oligocene. （3） For the Miocene, a widespread regional unconformity （ca. 23 Ma） in and adjacent to the plateau indicates comprehensive uplift of the plateau. This period is characterized by depressions （lakes） in the Tarim, Qaidam, Xining-Nanzhou, Qiangtang, and Hoh Xil. Lacustrine facies deposition expanded to peak in and adjacent to the plateau ca. 18-13 Ma, and north-south fault basins formed in southern Tibet ca. 13-10 Ma. All of these features indicate that the plateau uplifted to its peak and began to collapse. （4） Uplift and erosion occurred during the Pliocene in most parts of the plateau, except in the Hoh Xil-Qiangtang, Tarim, and Qaidam. The continuous uplift and intensive taphrogeny in the plateau divided the original large basin into small basins, deposition of lacustrine facies decreased considerably, and boulderstone accumulated, indicating a response to the overall uplift of the plateau. Here, we discuss the evolution of tectonic lithofacies paleogeography in Cenozoic and its response to the tectonic uplift of the Qinghai-Tibet Plateau in relation to the above characteristics. We have recognized five major uplift events, which occurred during 58-53 Ma, 45-30 Ma, 25-20 Ma, 13-7 Ma, and since 5 Ma. The results presented here indicate that the paleogeomorphic configurations of the Qinghai-Tibet Plateau turned over during the late Miocene, with high elevations in the east during the pre-Miocene switching to high contours in the west at the end of Miocene.展开更多
Late Carboniferous to Early Permian A-type granites are extensively distributed throughout the West Junggar region, NW China, and the Akebasitao pluton is extremely distinguished among these plutons. In this paper, we...Late Carboniferous to Early Permian A-type granites are extensively distributed throughout the West Junggar region, NW China, and the Akebasitao pluton is extremely distinguished among these plutons. In this paper, we reported new anisotropy of magnetic susceptible （AMS） data combine with detailed field study and audio magnetotelluric （AMT） sounding to assess the three-dimensional shape and magmatic emplacement mechanism of the Akebasitao pluton. The geological features and the AMT sounding indicate that the pluton had a slightly oblique movement of magma from northwest to southeast, which was most likely to correspond to an asymmetrical torch with a laccolith-shaped upper part, and a lower part formed by sub-vertical ＂root＂ that was located within its northwestern part, probably controlled by the NE-trending Anqi fault. The AMS fabrics of all the specimens reveal a low Pj value （mean of 1.02） and a low T value （mean of -0.024）, suggesting that the deformation of the AMS ellipsoid is relatively weak. The specimens exhibit both oblate and prolate shapes of the AMS ellipsoid. Magnetic lineations and foliations are randomly distributed throughout the pluton without any preferred orientation. These AMS patterns indicate that the pluton formed in a relatively stable structural environment with no regional extrusion. Therefore, we propose a complex emplacement process in which the magmas reached the shallower crust levels via deep-faults and subsequently occupied the room created by doming, accompanied by stoping near the pluton roof. Additionally, the regional tectonic setting was relatively stable during the emplacement of the Akebasitao pluton, indicating the termination of compressional orogeny during the late Late Carboniferous in the West Junggar region. This conclusion perfectly coincides with the regional tectonic paleogeography, magmatic system, and paleostress field.展开更多
By a detailed investigation of geometry and kinematics of the Shangma （商麻） fault in Dabieshan （大别山）, three different crust levels of extension movement have been recognized in sequence from the deep to the sh...By a detailed investigation of geometry and kinematics of the Shangma （商麻） fault in Dabieshan （大别山）, three different crust levels of extension movement have been recognized in sequence from the deep to the shallow：① low-angle ductile detachment shearing with top to the NW; ② low-angle normal fault with top to the NW or NWW in brittle or brittle-ductile transition domain; ③ high-angle brittle normal fault with top to the W or NWW. Two samples were chosen for zircon U-Pb age dating to constrain the activity age of the Shangma fault. A bedding intrusive granitoid pegmatite vein that is parallel to the foliation of the low-angle ductile detachment shear zone of the country rock exhibits a lotus-joint type of boudinage deformation, showing syn-tectonic emplacing at the end of the ductile deformation period and deformation in the brittle-ductile transition domain. The zircon U-Pb dating of this granitoid pegmatite vein gives an age of （125.9±4.2） Ma, which expresses the extension in the brittle-ductile transition domain of the Shangma fault. The other sample, which is collected from a granite pluton cutting the foliation of the low-angle ductile detachment shear zone, gives a zircon U-Pb age of （118.8±4.1） Ma, constraining the end of the ductile detachment shearing. Then the transformation age from ductile to brittle deformation can be constrained between 126-119 Ma. Combined with the previous researches, the formation of the Luotian （罗田） dome, which is locatedto the east of the Shangma fault, can be constrained during 150-126 Ma. This study gives a new time constraint to the evolution of the Dabie orogenic belt.展开更多
Multi-stage uplift of the Tibetan Plateau during the Cenozoic implies a complex geodynamic process.In this paper,we review main geodynamic models for the uplift of the plateau,and,in particular,analyze the spatio-temp...Multi-stage uplift of the Tibetan Plateau during the Cenozoic implies a complex geodynamic process.In this paper,we review main geodynamic models for the uplift of the plateau,and,in particular,analyze the spatio-temporal framework of the Cenozoic deformation structures,which are closely related to the deep geodynamic mechanism for the plateau uplift.From this perspective,significant change of the deformation regime over the Tibetan Plateau occurred by the middle-late Miocene,while thrust and thrust-folding system under NS compression was succeded by extension or stress-relaxation.Meanwhile,a series of large-scale strike-slip faults commenced or was kinemtically reversed.Based on a systematic synthesis of the structure deformation,magmatism,geomorphological process and geophysical exploration,we propose a periodical model of alternating crustal compression and extension for episodic uplift of the Tibetan Plateau.展开更多
Abstract: Zircon and apatite fission-track dating indicates that the exhumation of the Dabie Mountains tended to be accelerated in the Cenozoic and that the exhumation of the eastern Dabie Mountains was more and more ...Abstract: Zircon and apatite fission-track dating indicates that the exhumation of the Dabie Mountains tended to be accelerated in the Cenozoic and that the exhumation of the eastern Dabie Mountains was more and more intense from south to north, which is in accordance with the more and more intense dissection from south to north, as is reflected by the modern geomorphologic features of the Dabie Mountains. The accelerated exhumation during the Cenozoic was related to the high elevation of the Dabie Mountains resulting from Late Cretaceous-Palaeogene detachment faulting and subsequent fault-block uplift and subsidence. The average elevation at that time was at least about 660 m higher than that at the present. The intense exhumation lagged behind intense uplift.展开更多
The Hohxil region in the northern Qinghai-Tibet Plateau is occupied by numerous plateau lakes, which have long been inferred as being tectonic products. However, so far little evidence has been found to support this t...The Hohxil region in the northern Qinghai-Tibet Plateau is occupied by numerous plateau lakes, which have long been inferred as being tectonic products. However, so far little evidence has been found to support this tentative inference. Field survey and morphotectonic analysis of TM satellite images in the eastern segment of the Hohxil region revealed that Kusai Lake and Yelusu Lake are S- shaped pull-apart basins, which were dominated by left strike-slip master faults trending WNW-ESE. The pull-apart distances of the two lakes are analyzed to be 〈15-20 km and 15 km respectively. Based on studies of the faulting rate, the initiation ages of the pull-apart basins are suggested to be approximately in the Early Pleistocene. The pull-apart basin tectonics is further regarded as a common mechanism for the widely distributed large lake basins in the northern Qinghai-Tibet Plateau. Regional distribution of these pull-apart basins and their substantial intra-block slip suggest that a sinistral shear stress, which is independent of the distinguished strike-slip faults, has been imposed on across the northern Qinghai-Tibet Plateau. Thus, the intra-block slip may be an important expression of the eastward extrusion of the Plateau crustal material in accommodating the ongoing continent-continent convergence between India and Eurasia. The revelation of pull-apart tectonics within the Plateau hinterland provides field evidence and a possible style of deformation for the newly proposed continuous deformation by the global positioning system （GPS） measurement across the northern Qinghai-Tibet Plateau. A model, with respect to systematic tectonic landform development, for pull- apart basins is finally proposed.展开更多
Ophiolites represent on-land fragments of paleooceanic crust and have been recognized as one of the key markers of suture zones.Here,we provide new insights into the emplacement of ophiolitic mélanges based on de...Ophiolites represent on-land fragments of paleooceanic crust and have been recognized as one of the key markers of suture zones.Here,we provide new insights into the emplacement of ophiolitic mélanges based on detailed geological mapping and structural analysis in the West Junggar and Songpan-Ganzi-Bayan Har orogens(Fig.1 and Fig.2).The results show that some ophiolitic mélange belts cannot be regarded as suture zones.The distribution of these ophiolitic mélange belts are usually associated with the structural processes during the closure of remnant oceanic basins.After the remnant-oceanic basin is filled with thick clastic deposit,the oceanic lithosphere material as the base of the remnant basin can be injected into the overlying sedimentary strata through various faultings under the regional compressive stress,forming the remnant oceanic basintype ophiolitic mélange system with dispersive distribution characteristics.Combining with previous researches,the emplacement mechanism of ophiolitic mélanges can be divided into four categories:subduction type which oceanic lithosphere subducted beneath active continental margin,obduction type which oceanic lithosphere obducted over passive continental margin,collision type between two continental lithospheres,and closure type of remnant-oceanic basin(Fig.3).These different types of ophiolitic mélange belts will be superimposed and even re-emplacement by the tectonic processes of post-plate convergence,complicating their distribution.Therefore,identifying the emplacement mechanism type of ophiolitic mélange belts formed in different tectonic processes and backgrounds is of importance for understanding the process of ocean-continental transition and the evolution of orogenic belts.展开更多
The Longxinggou Nappe which is located in Guangshui county, north of Hubei province, has been first identified by our detail mapping. It is composed of lowgrade metamorphosed rocks of middle Proterozoic Shuixian group...The Longxinggou Nappe which is located in Guangshui county, north of Hubei province, has been first identified by our detail mapping. It is composed of lowgrade metamorphosed rocks of middle Proterozoic Shuixian group, late Proterozoic Yaolinghe group, Sinian Liantuo,Doushantuo and Dengying formations. It is quite different from the lower beds, middle.Proterozoic Hong’an epidote-amphibole facies metamorphose metapelite and metagranite. They are different not only in composition, metamorphic degree, but also in deformation forms. The Longxinggou nappe has characteristics both of ductile thrusting and ductile dextral strike-sliping, illustrating a transpressive deformation regime of middle crustal in the orogenic belt due to the oblique collision, between the Shuiying terrain and the Tongbai terrain during Caledonian period.展开更多
基金supported by the Foundation of Geological Survey of China (Nos.1212011121261,1212010733802)the National Natural Science Foundation (No.40921062)
文摘We have studied the evolution of the tectonic lithofacies paleogeography of Paleocene- Eocene, Oligocene, Miocene, and Pliocene of the Qinghai-Tibet Plateau by compiling data regarding the type, tectonic setting, and iithostratigraphic sequence of 98 remnant basins in the plateau area. Our results can be summarized as follows. （1） The Paleocene to Eocene is characterized by uplift and erosion in the Songpan-Garze and Gangdise belts, depression （lakes and pluvial plains） in eastern Tarim, Qaidam, Qiangtang, and Hoh Xil, and the Neo-Tethys Sea in the western and southern Qinghai-Tibet Plateau. （2） The Oligocene is characterized by uplift in the Gangdise--Himalaya and Karakorum regions （marked by the absence of sedimentation）, fluvial transport （originating eastward and flowing westward） in the Brahmaputra region （marked by the deposition of Dazhuka conglomerate）, uplift and erosion in western Kunlun and Songpan-Garze, and depression （lakes） in the Tarim, Qaidam, Qiangtang, and Hoh Xil. The Oligocene is further characterized by depressional littoral and neritic basins in southwestern Tarim, with marine facies deposition ceasing at the end of the Oligocene. （3） For the Miocene, a widespread regional unconformity （ca. 23 Ma） in and adjacent to the plateau indicates comprehensive uplift of the plateau. This period is characterized by depressions （lakes） in the Tarim, Qaidam, Xining-Nanzhou, Qiangtang, and Hoh Xil. Lacustrine facies deposition expanded to peak in and adjacent to the plateau ca. 18-13 Ma, and north-south fault basins formed in southern Tibet ca. 13-10 Ma. All of these features indicate that the plateau uplifted to its peak and began to collapse. （4） Uplift and erosion occurred during the Pliocene in most parts of the plateau, except in the Hoh Xil-Qiangtang, Tarim, and Qaidam. The continuous uplift and intensive taphrogeny in the plateau divided the original large basin into small basins, deposition of lacustrine facies decreased considerably, and boulderstone accumulated, indicating a response to the overall uplift of the plateau. Here, we discuss the evolution of tectonic lithofacies paleogeography in Cenozoic and its response to the tectonic uplift of the Qinghai-Tibet Plateau in relation to the above characteristics. We have recognized five major uplift events, which occurred during 58-53 Ma, 45-30 Ma, 25-20 Ma, 13-7 Ma, and since 5 Ma. The results presented here indicate that the paleogeomorphic configurations of the Qinghai-Tibet Plateau turned over during the late Miocene, with high elevations in the east during the pre-Miocene switching to high contours in the west at the end of Miocene.
基金funded by the China Geological Survey (Grant Nos.1212011120502,1212011220245)
文摘Late Carboniferous to Early Permian A-type granites are extensively distributed throughout the West Junggar region, NW China, and the Akebasitao pluton is extremely distinguished among these plutons. In this paper, we reported new anisotropy of magnetic susceptible （AMS） data combine with detailed field study and audio magnetotelluric （AMT） sounding to assess the three-dimensional shape and magmatic emplacement mechanism of the Akebasitao pluton. The geological features and the AMT sounding indicate that the pluton had a slightly oblique movement of magma from northwest to southeast, which was most likely to correspond to an asymmetrical torch with a laccolith-shaped upper part, and a lower part formed by sub-vertical ＂root＂ that was located within its northwestern part, probably controlled by the NE-trending Anqi fault. The AMS fabrics of all the specimens reveal a low Pj value （mean of 1.02） and a low T value （mean of -0.024）, suggesting that the deformation of the AMS ellipsoid is relatively weak. The specimens exhibit both oblate and prolate shapes of the AMS ellipsoid. Magnetic lineations and foliations are randomly distributed throughout the pluton without any preferred orientation. These AMS patterns indicate that the pluton formed in a relatively stable structural environment with no regional extrusion. Therefore, we propose a complex emplacement process in which the magmas reached the shallower crust levels via deep-faults and subsequently occupied the room created by doming, accompanied by stoping near the pluton roof. Additionally, the regional tectonic setting was relatively stable during the emplacement of the Akebasitao pluton, indicating the termination of compressional orogeny during the late Late Carboniferous in the West Junggar region. This conclusion perfectly coincides with the regional tectonic paleogeography, magmatic system, and paleostress field.
基金the National Key Science Foundation of China (No.40334037)the National Natural Science Foundation of China (No.40672137)
文摘By a detailed investigation of geometry and kinematics of the Shangma （商麻） fault in Dabieshan （大别山）, three different crust levels of extension movement have been recognized in sequence from the deep to the shallow：① low-angle ductile detachment shearing with top to the NW; ② low-angle normal fault with top to the NW or NWW in brittle or brittle-ductile transition domain; ③ high-angle brittle normal fault with top to the W or NWW. Two samples were chosen for zircon U-Pb age dating to constrain the activity age of the Shangma fault. A bedding intrusive granitoid pegmatite vein that is parallel to the foliation of the low-angle ductile detachment shear zone of the country rock exhibits a lotus-joint type of boudinage deformation, showing syn-tectonic emplacing at the end of the ductile deformation period and deformation in the brittle-ductile transition domain. The zircon U-Pb dating of this granitoid pegmatite vein gives an age of （125.9±4.2） Ma, which expresses the extension in the brittle-ductile transition domain of the Shangma fault. The other sample, which is collected from a granite pluton cutting the foliation of the low-angle ductile detachment shear zone, gives a zircon U-Pb age of （118.8±4.1） Ma, constraining the end of the ductile detachment shearing. Then the transformation age from ductile to brittle deformation can be constrained between 126-119 Ma. Combined with the previous researches, the formation of the Luotian （罗田） dome, which is locatedto the east of the Shangma fault, can be constrained during 150-126 Ma. This study gives a new time constraint to the evolution of the Dabie orogenic belt.
基金supported by the National Special Project on the Tibetan Plateau of the China Geological Survey (1212011121261, 1212010610103)the National Natural Science Foundation of China (Nos. 41202144, 40902060)
文摘Multi-stage uplift of the Tibetan Plateau during the Cenozoic implies a complex geodynamic process.In this paper,we review main geodynamic models for the uplift of the plateau,and,in particular,analyze the spatio-temporal framework of the Cenozoic deformation structures,which are closely related to the deep geodynamic mechanism for the plateau uplift.From this perspective,significant change of the deformation regime over the Tibetan Plateau occurred by the middle-late Miocene,while thrust and thrust-folding system under NS compression was succeded by extension or stress-relaxation.Meanwhile,a series of large-scale strike-slip faults commenced or was kinemtically reversed.Based on a systematic synthesis of the structure deformation,magmatism,geomorphological process and geophysical exploration,we propose a periodical model of alternating crustal compression and extension for episodic uplift of the Tibetan Plateau.
文摘Abstract: Zircon and apatite fission-track dating indicates that the exhumation of the Dabie Mountains tended to be accelerated in the Cenozoic and that the exhumation of the eastern Dabie Mountains was more and more intense from south to north, which is in accordance with the more and more intense dissection from south to north, as is reflected by the modern geomorphologic features of the Dabie Mountains. The accelerated exhumation during the Cenozoic was related to the high elevation of the Dabie Mountains resulting from Late Cretaceous-Palaeogene detachment faulting and subsequent fault-block uplift and subsidence. The average elevation at that time was at least about 660 m higher than that at the present. The intense exhumation lagged behind intense uplift.
基金supported by China Geological Survey (No.1212010610103 and 200313000005)the National Natural Science Foundation of China (No.40672137 and 40372104).
文摘The Hohxil region in the northern Qinghai-Tibet Plateau is occupied by numerous plateau lakes, which have long been inferred as being tectonic products. However, so far little evidence has been found to support this tentative inference. Field survey and morphotectonic analysis of TM satellite images in the eastern segment of the Hohxil region revealed that Kusai Lake and Yelusu Lake are S- shaped pull-apart basins, which were dominated by left strike-slip master faults trending WNW-ESE. The pull-apart distances of the two lakes are analyzed to be 〈15-20 km and 15 km respectively. Based on studies of the faulting rate, the initiation ages of the pull-apart basins are suggested to be approximately in the Early Pleistocene. The pull-apart basin tectonics is further regarded as a common mechanism for the widely distributed large lake basins in the northern Qinghai-Tibet Plateau. Regional distribution of these pull-apart basins and their substantial intra-block slip suggest that a sinistral shear stress, which is independent of the distinguished strike-slip faults, has been imposed on across the northern Qinghai-Tibet Plateau. Thus, the intra-block slip may be an important expression of the eastward extrusion of the Plateau crustal material in accommodating the ongoing continent-continent convergence between India and Eurasia. The revelation of pull-apart tectonics within the Plateau hinterland provides field evidence and a possible style of deformation for the newly proposed continuous deformation by the global positioning system （GPS） measurement across the northern Qinghai-Tibet Plateau. A model, with respect to systematic tectonic landform development, for pull- apart basins is finally proposed.
基金granted by the China Geological Survey(Grand No.1212011220245,DD20179607,DD20160060)
文摘Ophiolites represent on-land fragments of paleooceanic crust and have been recognized as one of the key markers of suture zones.Here,we provide new insights into the emplacement of ophiolitic mélanges based on detailed geological mapping and structural analysis in the West Junggar and Songpan-Ganzi-Bayan Har orogens(Fig.1 and Fig.2).The results show that some ophiolitic mélange belts cannot be regarded as suture zones.The distribution of these ophiolitic mélange belts are usually associated with the structural processes during the closure of remnant oceanic basins.After the remnant-oceanic basin is filled with thick clastic deposit,the oceanic lithosphere material as the base of the remnant basin can be injected into the overlying sedimentary strata through various faultings under the regional compressive stress,forming the remnant oceanic basintype ophiolitic mélange system with dispersive distribution characteristics.Combining with previous researches,the emplacement mechanism of ophiolitic mélanges can be divided into four categories:subduction type which oceanic lithosphere subducted beneath active continental margin,obduction type which oceanic lithosphere obducted over passive continental margin,collision type between two continental lithospheres,and closure type of remnant-oceanic basin(Fig.3).These different types of ophiolitic mélange belts will be superimposed and even re-emplacement by the tectonic processes of post-plate convergence,complicating their distribution.Therefore,identifying the emplacement mechanism type of ophiolitic mélange belts formed in different tectonic processes and backgrounds is of importance for understanding the process of ocean-continental transition and the evolution of orogenic belts.
文摘The Longxinggou Nappe which is located in Guangshui county, north of Hubei province, has been first identified by our detail mapping. It is composed of lowgrade metamorphosed rocks of middle Proterozoic Shuixian group, late Proterozoic Yaolinghe group, Sinian Liantuo,Doushantuo and Dengying formations. It is quite different from the lower beds, middle.Proterozoic Hong’an epidote-amphibole facies metamorphose metapelite and metagranite. They are different not only in composition, metamorphic degree, but also in deformation forms. The Longxinggou nappe has characteristics both of ductile thrusting and ductile dextral strike-sliping, illustrating a transpressive deformation regime of middle crustal in the orogenic belt due to the oblique collision, between the Shuiying terrain and the Tongbai terrain during Caledonian period.
