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
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
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
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.
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 ℃.
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.
