A high-angle ductile thrusting deformation with top-to-the-north movement penetratively developed in the Proterozoic-Early Paleozoic metamorphic rocks along the Central East Kunlun belt. The deformed rocks suffered ep...A high-angle ductile thrusting deformation with top-to-the-north movement penetratively developed in the Proterozoic-Early Paleozoic metamorphic rocks along the Central East Kunlun belt. The deformed rocks suffered epidote-amphibolite facies metamorphism. On the basis of our previous study, we present more data in this paper to further support that the ducdle thrust deformation occurred in the later Caledonian and more detailed information about the deformation. A zircon U-Pb concordant age of 446±2.2 Ma of a deformed granodiorite in the ductile thrust zone was obtained and can be interpreted as the lower limit of the deformation. A syntectonically crystallized and also strongly deformed hornblende Ar/ Ar dating gives an Ar/Ar plateau age of 426.5±3.8 Ma, which represents the deformation age. A strongly orientated muscovite gives an Ar/Ar plateau age of 408±1.6Ma, representing the cooling age after the peak temperature, constraining the upper limit of the ductile thrust deformation. This ductile thrust deformation can be interpreted as the result of the closing of the Central East Kunlun archipelago ocean. To the north, Ar/Ar plateau ages of 382.9±0.2 Ma and 386.8±0.8 Ma of muscovite in the deformed Xiaomiao Group represent the uplift cooling ages of deeper rocks after the thrusting movement. The original thrusting foliation has a low angle. A rotation model was put forward to explain the development of the foliation from the original low-angle to present high-angle dipping.展开更多
Using the snow cover fi＇action （SNC） output from eight WCRP CMIP3 climate models under SRES A2, A1B, and B1 scenarios, the future trend of SNC over East Asia is analyzed. Results show that SNC is likely to decrease...Using the snow cover fi＇action （SNC） output from eight WCRP CMIP3 climate models under SRES A2, A1B, and B1 scenarios, the future trend of SNC over East Asia is analyzed. Results show that SNC is likely to decrease in East Asia, with the fastest decrease in spring, then winter and autumn, and the slowest in summer, In spring and winter the SNC decreases faster in the Qinghai-Xizang Plateau than in northern East Asia, while in autumn there is little difference between them. Among the various scenarios, SRES A2 has the largest decrease trend, then A1B, and B1 has the smallest trend. The decrease in SNC is mainly caused by the changes in surface air temperature and snowfall, which contribute differently to the SNC trends in different regions and seasons.展开更多
Wulonggou deposit is a large tectonoalteration gold deposit which is discovered in 1980s in East Kunlun area of Qinghai Province. The ore bodies occur in the rock series of metamorphic basement of Lower Proterozoic an...Wulonggou deposit is a large tectonoalteration gold deposit which is discovered in 1980s in East Kunlun area of Qinghai Province. The ore bodies occur in the rock series of metamorphic basement of Lower Proterozoic and granitoid Variscan to Lower Mesozoic. The shape, attitude and scale of the ore bodies are strictly controlled by the tectonoalteration belts, which show a typical characteristic of tectonoalteration deposits. A detailed discussion on typical deposits could also contribute to the evaluation of the regional gold metallogenic potential in East Kunlun area, and provide a direction for further gold prospecting between and/or near Kunzhong and Kunnan faults, and in areas of granitoid distribution of Variscan and Lower Mesozoic.展开更多
The Qinghai-Tibet Plateau has developed into a vast fortress-like structure that has recently presented a barrier limiting the egress of moisture-bearing air masses. Lower sea levels also affected the climate. This pa...The Qinghai-Tibet Plateau has developed into a vast fortress-like structure that has recently presented a barrier limiting the egress of moisture-bearing air masses. Lower sea levels also affected the climate. This paper examines their effects on the current evidence for the timing of past glaciations, and the development and evolution of permafrost. There are two theories regarding glaciation on the Qinghai-Tibet Plateau （QTP）. Kuhle suggested that there was a major, unified ice-cap during the Last Glacial Maximum （LGM）, whereas major Chinese glaciologists and others have not found or verified reliable evidence for this per se. There have been limited glaciations during the last 1.1 Ma B.P. but with increasing dominance of permafrost including both primary and secondary tessellons infilled with rock, sand or loess. The East Asia Monsoon was absent in this area during the main LGM, starting at 〉30 ka B.P. on the plateau, with sufficient precipitation reappearing about 19 ka B.P. to produce ice-wedges. A weak Megathermal event took place between 8.5 and 6.0 ka B.P., followed by Neoglacial events exhibiting peak cold at 5.3-4.7 ka, 3.1-1.5 ka, and the Little Ice Age （LIA） after 0.7 ka. Subsequently, mean annual air temperature has increased by 4 ℃.展开更多
A near NS-strike east-dipping normal fault is developed on the western side of Wenquan graben in the central Qinghai-Xizang(Tibet) Plateau. It is the western marginal fault of the graben and has been intensely active....A near NS-strike east-dipping normal fault is developed on the western side of Wenquan graben in the central Qinghai-Xizang(Tibet) Plateau. It is the western marginal fault of the graben and has been intensely active. It is a product of the near EW extension and deformation of the central northern Qinghai-Xizang(Tibet) Plateau since the late Cenozoic under the effect of the collision of the India and Eurasia plates. Since the late Cenozoic, the maximum vertical displacement on the fault was greater than 2.1km, and the dislocated Mesozoic fold stratum reveals a maximum accumulative throw of 6.0±2.2km. Quaternary faulting took place many times along the fault, creating multi-set piedmont fault facets and multi-level fault scarplets. According to the height of fault scarps that result from the vertical offset of the late Quaternary strata and geomorphic provinces, the maximum slip rate of the fault is estimated to have been less than 1.2mm/a since the late Quaternary, averaging 0.45mm/a. The trenching across the fault reveals that at least 3 paleoearthquakes of varied magnitudes have occurred since the late Epipleistocene. In view of the characteristics of Cenozoic faulting, it is concluded that the fault will act as a dominant seismogenic fault for earthquakes of M6.0 to M7.0 that are most likely to occur in the future.展开更多
There were more expounding to north—west (west) trend fault and north\|east trend fault within Qiangtang Basin, North Part of Tibet, in the past literature. With increasing of geophysical exploration data, nearly eas...There were more expounding to north—west (west) trend fault and north\|east trend fault within Qiangtang Basin, North Part of Tibet, in the past literature. With increasing of geophysical exploration data, nearly east\|west trend structure began to be taken note to. Since the year of 1995, by a synthetic study to geophysical and geological data, that south\|north trend faulted structures are well developed. These structures should be paid much more attention to, because they have important theoretical meaning and practical significance.1 Spreading of south\|north faulted structure belt According to different geological and geophysical data, the six larger scale nearly south\|north faulted structure belt could be distinguished within the scope of east longitude 84°～96° and near Qiangtang Basin. The actual location of the six belts are nearly located in the west of the six meridian of east longitude 85°,87°,89°,91°,93°,95° or located near these meridian. The six south\|north faulted structure belts spread in the same interval with near 2° longitude interval. The more clear and much more significance of south\|north trend faulted structure belts are the two S—N trend faulted structure belts of east longitude 87° and 89°. There are S—N trend faulted structure belts in the west of east longitude 83°,81°, or near the longitudes. The structure belts spreading features,manifestation,geological function and its importance, and inter texture and structure are not exactly so same. The structure belts all different degree caused different region of geological structure or gravity field and magnetic field. There is different scale near S—N trend faulted structure belt between the belts.展开更多
Yushu Tibetan Autonomous Prefecture is situated in the southwestern area of Qinghai Province,the central region of the Qinghai-Tibet Plateau.It connects with Haixi Mongolian and Tibetan Autonomous Prefecture to the no...Yushu Tibetan Autonomous Prefecture is situated in the southwestern area of Qinghai Province,the central region of the Qinghai-Tibet Plateau.It connects with Haixi Mongolian and Tibetan Autonomous Prefecture to the north and Guoluo Tibetan Autonomous Prefecture to the east.展开更多
Qinghai Lake, China, is located near the northern limit of the East Asian summer monsoon （EASM） and thus is an ideal region for studies of past monsoonal changes. However, isotope records from this region reflect th...Qinghai Lake, China, is located near the northern limit of the East Asian summer monsoon （EASM） and thus is an ideal region for studies of past monsoonal changes. However, isotope records from this region reflect the combined effects of multiple climatic factors, and make climatic interpretations difficult. The authors use multi-proxy records, generated from the same sediment core from Qinghai Lake, to disentangle these multiple effects in isotope records and to infer EASM variability during the late Holocene. Records of leaf wax （C2s） δD, lake carbonate 5180 and the Dunde ice core δ18O all indicate a millennial-scale depletion of mean isotopic values at -1500-1250 years before present. Compared with independent lake temperature and salinity records, the authors suggest that this depletion of long-term mean isotopic values must have resulted from changes in moisture sources in this region. In contrast, the authors attribute high-frequency （centennial timescale） C2s δD and ice core δ18O variability dominantly to a temperature effect. The multiproxy records provide a coherent picture in that many aspects of this regional climate （temperature, dryness, and moisture source） are strongly linked to the EASM variability.展开更多
Qiangtang Massif is located in the hinterland of Qinghai—Tibet plateau, which belong to the mid\|east section of Tethys Tectonic Domain.1 Features of the whole texture and structure of Qiangtang massif By synthetic a...Qiangtang Massif is located in the hinterland of Qinghai—Tibet plateau, which belong to the mid\|east section of Tethys Tectonic Domain.1 Features of the whole texture and structure of Qiangtang massif By synthetic analysis of gravity,magnetic field,MT,seismic surveying,etc. Geophysical data, the massif, lied in the tectonic setting and geodynamic setting mingled by the south,north tectonic belts, have the features of massif,basin and tectonic belt three forming an organic whole,multi\|degree coupling in plane and section with division of region in south\|north trend,division of block\|fault in east\|west trend,division of sphere\|layer in vertical direction. (1) Belting in south\|north trend: Qiangtang massif could be divided into four units from north to south, that is north edge doming zone, west part doming area,Qiangtang Basin and south edge doming zone. Qiangtang Basin also can be divided into four tectonic units—north Qiangtang down\|warping region, middle downing zone, south Qiangtang down\|warping and east part slope region. The near east\|west trend tectonic zones are well developed. There is aero\|magnetic anomaly distributed in belting with east\|west trend but also concentrated in section. Gravity anomaly is high in the south\|west part and low in the northeast part. Inter\|crust low resistance layer alternately distributed with high and low belting of sou th\|north trend in plane.展开更多
Climate in Eastern Asia is composed of monsoon climate in the east,arid and semi-arid climate in the north and west,and the cold and dry climate of Qinghai-Tibetan Plateau in the southwest.The underlying causes for th...Climate in Eastern Asia is composed of monsoon climate in the east,arid and semi-arid climate in the north and west,and the cold and dry climate of Qinghai-Tibetan Plateau in the southwest.The underlying causes for the evolution of East Asian climate during late Cenozoic have long been investigated and debated,particularly with regards to the role played by the Qinghai-Tibetan Plateau uplift and the global cooling.In this paper,we reviewed major research developments in this area,and summarized the important results.Based on a synthesis of data,we propose that the Qinghai-Tibetan Plateau uplift alone cannot fully explain the formation of monsoon and arid climates in Eastern Asia during the past 22–25 Ma.Other factors such as the global ice volume and high-latitude temperature changes have also played a vital role.Moreover,atmospheric CO2changes may have modulated the monsoon and dry climate changes by affecting the location of the inter-tropical convergence zone(ITCZ),which controls the monsoon precipitation zone and the track of the East Asian winter monsoon during late Cenozoic.The integration of high-resolution geological record and numerical paleoclimate modeling could make new contributions to understanding the climate evolution and variation in eastern Asia in future studies.It could facilitate the investigation of the regional differences in East Asian environmental changes and the asynchronous nature between the uplift of Qinghai-Tibetan Plateau and their climatic effects.These would be the keys to understanding underlying driving forces for the evolution of the East Asian climate.展开更多
During the period from 25 to 17 Ma BP, when the second plateau uplifting, i.e. the second phase of the Himalaya movement, occurred, the Qinghai-Xizang Plateau reached an altitude high enough to change the situation of...During the period from 25 to 17 Ma BP, when the second plateau uplifting, i.e. the second phase of the Himalaya movement, occurred, the Qinghai-Xizang Plateau reached an altitude high enough to change the situation of the general circulation. Such an effect of the plateau on the atmospheric circulation was accompanied by the warming of the tropical ocean, the enhancement of the cross equatorial current, the enlargement of the marginal sea basins in the cast-southeastern Asia, the westward extending of the Asian continent and the regression of the Paratethys Sea. As a result, the thermal difference was enlarged, and the air currents were enhanced between continents and oceans; finally the Asian monsoon system, mainly the summer monsoon, was initiated. The former planet wind system was then substituted by the monsoon system, and this caused the important environmental changes, such as the large shrinkage of the dry steppe in Central Asia, and the extension of the humid forest zone in East Asia. Those展开更多
文摘A high-angle ductile thrusting deformation with top-to-the-north movement penetratively developed in the Proterozoic-Early Paleozoic metamorphic rocks along the Central East Kunlun belt. The deformed rocks suffered epidote-amphibolite facies metamorphism. On the basis of our previous study, we present more data in this paper to further support that the ducdle thrust deformation occurred in the later Caledonian and more detailed information about the deformation. A zircon U-Pb concordant age of 446±2.2 Ma of a deformed granodiorite in the ductile thrust zone was obtained and can be interpreted as the lower limit of the deformation. A syntectonically crystallized and also strongly deformed hornblende Ar/ Ar dating gives an Ar/Ar plateau age of 426.5±3.8 Ma, which represents the deformation age. A strongly orientated muscovite gives an Ar/Ar plateau age of 408±1.6Ma, representing the cooling age after the peak temperature, constraining the upper limit of the ductile thrust deformation. This ductile thrust deformation can be interpreted as the result of the closing of the Central East Kunlun archipelago ocean. To the north, Ar/Ar plateau ages of 382.9±0.2 Ma and 386.8±0.8 Ma of muscovite in the deformed Xiaomiao Group represent the uplift cooling ages of deeper rocks after the thrusting movement. The original thrusting foliation has a low angle. A rotation model was put forward to explain the development of the foliation from the original low-angle to present high-angle dipping.
基金supported by the National Key Science and Technology Program of Ministry of Science and Technology of China (Grant No. 2007BAC03A01)
文摘Using the snow cover fi＇action （SNC） output from eight WCRP CMIP3 climate models under SRES A2, A1B, and B1 scenarios, the future trend of SNC over East Asia is analyzed. Results show that SNC is likely to decrease in East Asia, with the fastest decrease in spring, then winter and autumn, and the slowest in summer, In spring and winter the SNC decreases faster in the Qinghai-Xizang Plateau than in northern East Asia, while in autumn there is little difference between them. Among the various scenarios, SRES A2 has the largest decrease trend, then A1B, and B1 has the smallest trend. The decrease in SNC is mainly caused by the changes in surface air temperature and snowfall, which contribute differently to the SNC trends in different regions and seasons.
文摘Wulonggou deposit is a large tectonoalteration gold deposit which is discovered in 1980s in East Kunlun area of Qinghai Province. The ore bodies occur in the rock series of metamorphic basement of Lower Proterozoic and granitoid Variscan to Lower Mesozoic. The shape, attitude and scale of the ore bodies are strictly controlled by the tectonoalteration belts, which show a typical characteristic of tectonoalteration deposits. A detailed discussion on typical deposits could also contribute to the evaluation of the regional gold metallogenic potential in East Kunlun area, and provide a direction for further gold prospecting between and/or near Kunzhong and Kunnan faults, and in areas of granitoid distribution of Variscan and Lower Mesozoic.
文摘The Qinghai-Tibet Plateau has developed into a vast fortress-like structure that has recently presented a barrier limiting the egress of moisture-bearing air masses. Lower sea levels also affected the climate. This paper examines their effects on the current evidence for the timing of past glaciations, and the development and evolution of permafrost. There are two theories regarding glaciation on the Qinghai-Tibet Plateau （QTP）. Kuhle suggested that there was a major, unified ice-cap during the Last Glacial Maximum （LGM）, whereas major Chinese glaciologists and others have not found or verified reliable evidence for this per se. There have been limited glaciations during the last 1.1 Ma B.P. but with increasing dominance of permafrost including both primary and secondary tessellons infilled with rock, sand or loess. The East Asia Monsoon was absent in this area during the main LGM, starting at 〉30 ka B.P. on the plateau, with sufficient precipitation reappearing about 19 ka B.P. to produce ice-wedges. A weak Megathermal event took place between 8.5 and 6.0 ka B.P., followed by Neoglacial events exhibiting peak cold at 5.3-4.7 ka, 3.1-1.5 ka, and the Little Ice Age （LIA） after 0.7 ka. Subsequently, mean annual air temperature has increased by 4 ℃.
文摘A near NS-strike east-dipping normal fault is developed on the western side of Wenquan graben in the central Qinghai-Xizang(Tibet) Plateau. It is the western marginal fault of the graben and has been intensely active. It is a product of the near EW extension and deformation of the central northern Qinghai-Xizang(Tibet) Plateau since the late Cenozoic under the effect of the collision of the India and Eurasia plates. Since the late Cenozoic, the maximum vertical displacement on the fault was greater than 2.1km, and the dislocated Mesozoic fold stratum reveals a maximum accumulative throw of 6.0±2.2km. Quaternary faulting took place many times along the fault, creating multi-set piedmont fault facets and multi-level fault scarplets. According to the height of fault scarps that result from the vertical offset of the late Quaternary strata and geomorphic provinces, the maximum slip rate of the fault is estimated to have been less than 1.2mm/a since the late Quaternary, averaging 0.45mm/a. The trenching across the fault reveals that at least 3 paleoearthquakes of varied magnitudes have occurred since the late Epipleistocene. In view of the characteristics of Cenozoic faulting, it is concluded that the fault will act as a dominant seismogenic fault for earthquakes of M6.0 to M7.0 that are most likely to occur in the future.
文摘There were more expounding to north—west (west) trend fault and north\|east trend fault within Qiangtang Basin, North Part of Tibet, in the past literature. With increasing of geophysical exploration data, nearly east\|west trend structure began to be taken note to. Since the year of 1995, by a synthetic study to geophysical and geological data, that south\|north trend faulted structures are well developed. These structures should be paid much more attention to, because they have important theoretical meaning and practical significance.1 Spreading of south\|north faulted structure belt According to different geological and geophysical data, the six larger scale nearly south\|north faulted structure belt could be distinguished within the scope of east longitude 84°～96° and near Qiangtang Basin. The actual location of the six belts are nearly located in the west of the six meridian of east longitude 85°,87°,89°,91°,93°,95° or located near these meridian. The six south\|north faulted structure belts spread in the same interval with near 2° longitude interval. The more clear and much more significance of south\|north trend faulted structure belts are the two S—N trend faulted structure belts of east longitude 87° and 89°. There are S—N trend faulted structure belts in the west of east longitude 83°,81°, or near the longitudes. The structure belts spreading features,manifestation,geological function and its importance, and inter texture and structure are not exactly so same. The structure belts all different degree caused different region of geological structure or gravity field and magnetic field. There is different scale near S—N trend faulted structure belt between the belts.
文摘Yushu Tibetan Autonomous Prefecture is situated in the southwestern area of Qinghai Province,the central region of the Qinghai-Tibet Plateau.It connects with Haixi Mongolian and Tibetan Autonomous Prefecture to the north and Guoluo Tibetan Autonomous Prefecture to the east.
基金US NSF grants to Yong- song Huang (ESH-0318050, 0318123, 0402383 and OPP- 0520718)
文摘Qinghai Lake, China, is located near the northern limit of the East Asian summer monsoon （EASM） and thus is an ideal region for studies of past monsoonal changes. However, isotope records from this region reflect the combined effects of multiple climatic factors, and make climatic interpretations difficult. The authors use multi-proxy records, generated from the same sediment core from Qinghai Lake, to disentangle these multiple effects in isotope records and to infer EASM variability during the late Holocene. Records of leaf wax （C2s） δD, lake carbonate 5180 and the Dunde ice core δ18O all indicate a millennial-scale depletion of mean isotopic values at -1500-1250 years before present. Compared with independent lake temperature and salinity records, the authors suggest that this depletion of long-term mean isotopic values must have resulted from changes in moisture sources in this region. In contrast, the authors attribute high-frequency （centennial timescale） C2s δD and ice core δ18O variability dominantly to a temperature effect. The multiproxy records provide a coherent picture in that many aspects of this regional climate （temperature, dryness, and moisture source） are strongly linked to the EASM variability.
文摘Qiangtang Massif is located in the hinterland of Qinghai—Tibet plateau, which belong to the mid\|east section of Tethys Tectonic Domain.1 Features of the whole texture and structure of Qiangtang massif By synthetic analysis of gravity,magnetic field,MT,seismic surveying,etc. Geophysical data, the massif, lied in the tectonic setting and geodynamic setting mingled by the south,north tectonic belts, have the features of massif,basin and tectonic belt three forming an organic whole,multi\|degree coupling in plane and section with division of region in south\|north trend,division of block\|fault in east\|west trend,division of sphere\|layer in vertical direction. (1) Belting in south\|north trend: Qiangtang massif could be divided into four units from north to south, that is north edge doming zone, west part doming area,Qiangtang Basin and south edge doming zone. Qiangtang Basin also can be divided into four tectonic units—north Qiangtang down\|warping region, middle downing zone, south Qiangtang down\|warping and east part slope region. The near east\|west trend tectonic zones are well developed. There is aero\|magnetic anomaly distributed in belting with east\|west trend but also concentrated in section. Gravity anomaly is high in the south\|west part and low in the northeast part. Inter\|crust low resistance layer alternately distributed with high and low belting of sou th\|north trend in plane.
基金supported by the Global Change Research Program of Ministry of Science and Technology of China(Grant No.2010CB950200)National Natural Science Foundation of China(Grant No.40930103)
文摘Climate in Eastern Asia is composed of monsoon climate in the east,arid and semi-arid climate in the north and west,and the cold and dry climate of Qinghai-Tibetan Plateau in the southwest.The underlying causes for the evolution of East Asian climate during late Cenozoic have long been investigated and debated,particularly with regards to the role played by the Qinghai-Tibetan Plateau uplift and the global cooling.In this paper,we reviewed major research developments in this area,and summarized the important results.Based on a synthesis of data,we propose that the Qinghai-Tibetan Plateau uplift alone cannot fully explain the formation of monsoon and arid climates in Eastern Asia during the past 22–25 Ma.Other factors such as the global ice volume and high-latitude temperature changes have also played a vital role.Moreover,atmospheric CO2changes may have modulated the monsoon and dry climate changes by affecting the location of the inter-tropical convergence zone(ITCZ),which controls the monsoon precipitation zone and the track of the East Asian winter monsoon during late Cenozoic.The integration of high-resolution geological record and numerical paleoclimate modeling could make new contributions to understanding the climate evolution and variation in eastern Asia in future studies.It could facilitate the investigation of the regional differences in East Asian environmental changes and the asynchronous nature between the uplift of Qinghai-Tibetan Plateau and their climatic effects.These would be the keys to understanding underlying driving forces for the evolution of the East Asian climate.
基金Project supported by the National Climbing Project and Chinese Academy of Sciences (KZ951-A1-204).
文摘During the period from 25 to 17 Ma BP, when the second plateau uplifting, i.e. the second phase of the Himalaya movement, occurred, the Qinghai-Xizang Plateau reached an altitude high enough to change the situation of the general circulation. Such an effect of the plateau on the atmospheric circulation was accompanied by the warming of the tropical ocean, the enhancement of the cross equatorial current, the enlargement of the marginal sea basins in the cast-southeastern Asia, the westward extending of the Asian continent and the regression of the Paratethys Sea. As a result, the thermal difference was enlarged, and the air currents were enhanced between continents and oceans; finally the Asian monsoon system, mainly the summer monsoon, was initiated. The former planet wind system was then substituted by the monsoon system, and this caused the important environmental changes, such as the large shrinkage of the dry steppe in Central Asia, and the extension of the humid forest zone in East Asia. Those
