This paper report paleomagnetic data from late Cretaceous diorite dykes that sub-vertically intrude granodiorites in the eastern Gangdese belt near the city of Lhasa.Our research goals are to provide further constrain...This paper report paleomagnetic data from late Cretaceous diorite dykes that sub-vertically intrude granodiorites in the eastern Gangdese belt near the city of Lhasa.Our research goals are to provide further constraints on pre-collisional structure of the southern margin of Asia and the onset of the India-Asia collision.Magnetite is identified as the main magnetic carrier in our study.The magnetite shows no evidence of metamorphism or alteration as determined from optical and scanning electron microscope observations.A strong mineral orientation is revealed by anisotropy of magnetic susceptibility analysis both for the intruded dykes and the country rocks.The authors interpret this AMS fabric to have formed during intrusion rather than deformation.Fifteen of 23 sites yield acceptable site mean characteristic remanences with dual polarities.A scatter analysis of the virtual geomagnetic poles suggests that the mean result adequately averaged paleosecular variation.The paleomagnetic pole from the Gangdese dykes yields a paleolatitude of 14.3°N±5.8°N for the southern margin of Asia near Lhasa.The paleolatitude corresponds to an in-between position of the Lhasa terrane during about 130‒60 Ma.Furthermore,the mean declination of the characteristic remanent magnetization reveals a significant counterclockwise rotation of 18°±9°for the sampling location since about 83 Ma.In the light of tectonic setting of the dykes,the strike of the southern margin of Asia near Lhasa is restored to trend approximately about 310°,which is compatible with the hypothesis that the southern margin of Eurasia had a quasi-linear structure prior to its collision with India.展开更多
This is a new report on the early Eocene radiolarian fauna from the Sangdanlin section in the Gyirong region, along the southern margin of the Yarlung Zangbo Suture Zone. The Sangdanlin section measured in this study ...This is a new report on the early Eocene radiolarian fauna from the Sangdanlin section in the Gyirong region, along the southern margin of the Yarlung Zangbo Suture Zone. The Sangdanlin section measured in this study is divided into three lithostratigraphic units from bottom to top: the Zongzhuo, Sangdanlin, and Zheya formations. Abundant radiolarian fossils were obtained from the Sangdanlin section and 54 species of 30 genera were identified and assigned as follows: Cryptamphorella conara-C. macropora the late Cretaceous Zone and Amphis_phaera coronate, Bur)ella tetradica-Bekoma campechensis, and B.bidartensis-B. divaricata the Paleocene-early Eocene Interval Zones. The Paleocene- early Eocene radiolarian zones are comparable to the radiolarian zones RP4-RP8 in New Zealand. Based on the data of radiolaria and lithofacies, it is suggested that the Zongzhuo Formation should be deposited along the base of the north-facing, continental slope of the Greater Indian continental margin, and the Sangdanlin Formation should be a deep marine, sedimentary sequence located in a foreland basin. The early Eocene radiolarian fauna in the Sangdanlin Formation constrains the initial age of the India-Asia collision to no later than 53.6 Ma.展开更多
Identifying when, where, and how India and Asia collided is a prerequisite to better understand the evolution of the Himalayan-Tibetan Plateau. Whereas with essentially the same published paleomagnetic data, a large r...Identifying when, where, and how India and Asia collided is a prerequisite to better understand the evolution of the Himalayan-Tibetan Plateau. Whereas with essentially the same published paleomagnetic data, a large range of different India-Asia collision models have been proposed in the literature. Based upon the premise of a northwards-moving Indian plate during the Cretaceous times, we analyze the significant variations in relative paleolatitude produced by a nearly 90° counterclockwise(CCW)rotation of the plate itself during the Cretaceous. Interestingly, recent studies proposed a dual-collision process with a Greater India basin or post-Neo-Tethyan ocean for the India-Asia collision, mainly in the light of divergent Cretaceous paleolatitude differences of the Tethyan Himalaya between the observed values and expected ones computed from the apparent polar wander path of the Indian plate. However, we find that these varied paleolatitude differences are mainly resulted from a nearly 90° CCW rotation of a rigid/quasi-rigid Greater Indian plate during the Cretaceous. On the other hand, when the Indian craton and Tethyan Himalaya moved as two individual blocks rather than a united rigid/quasi-rigid Greater Indian plate before the India-Asia collision, current available Cretaceous paleomagnetic data permit only multiple paleogeographic solutions for the tectonic relationship between the Indian plate and the Tethyan Himalayan terrane. We therefore argue that the tectonic relationship between the Indian plate and the Tethyan Himalayan terrane cannot be uniquely constrained by current paleomagnetic data in the absence of sufficient geological evidence, and the so-called Greater India basin model is just one of the ideal scenarios.展开更多
Placing precise constraints on the timing of the India-Asia continental collision is essential to understand the successive geological and geomorphological evolution of the orogenic belt as well as the uplift mechanis...Placing precise constraints on the timing of the India-Asia continental collision is essential to understand the successive geological and geomorphological evolution of the orogenic belt as well as the uplift mechanism of the Tibetan Plateau and their effects on climate,environment and life.Based on the extensive study of the sedimentary record on both sides of the Yarlung-Zangbo suture zone in Tibet,we review here the present state of knowledge on the timing of collision onset,discuss its possible diachroneity along strike,and reconstruct the early structural and topographic evolution of the Himalayan collided range.We define continent-continent collision as the moment when the oceanic crust is completely consumed at one point where the two continental margins come into contact.We use two methods to constrain the timing of collision onset:(1) dating the provenance change from Indian to Asian recorded by deep-water turbidites near the suture zone,and(2) dating the age of unconformities on both sides of the suture zone.The first method allowed us to constrain precisely collision onset as middle Palaeocene(59±l Ma).Marine sedimentation persisted in the collisional zone for another 20-25 Ma locally in southern Tibet,and molassic-type deposition in the Indian foreland basin did not begin until another 10-15 Ma later.Available sedimentary evidence failed to firmly document any significant diachroneity of collision onset from the central Himalaya to the western Himalaya and Pakistan so far.Based on the Cenozoic stratigraphic record of the Tibetan Himalaya,four distinct stages can be identified in the early evolution of the Himalayan orogen:(1) middle Palaeocene-early Eocene earliest Eohimalayan stage(from 59 to 52 Ma):collision onset and filling of the deep-water trough along the suture zone while carbonate platform sedimentation persisted on the inner Indian margin;(2) early-middle Eocene early Eohimalayan stage(from 52 to 41 or 35 Ma):filling of intervening seaways and cessation of marine sedimentation;(3) late Eocene-Oligocene late Eohimalayan stage(from 41 to 25 Ma):huge gap in the sedimentary record both in the collision zone and in the Indian foreland;and(4) late Oligocene-early Miocene early Neohimalayan stage(from 26 to 17 Ma):rapid Himalayan growth and onset of molasse-type sedimentation in the Indian foreland basin.展开更多
目的:介绍顺势疗法在南亚地区的发展现状,为我国学术界了解顺势疗法提供参考。方法:本文以History and Status of Homeopathy around the world《环球顺势疗法的历史和现状》为研究资料,从使用情况、教学情况、研究机构等方面,对顺势疗...目的:介绍顺势疗法在南亚地区的发展现状,为我国学术界了解顺势疗法提供参考。方法:本文以History and Status of Homeopathy around the world《环球顺势疗法的历史和现状》为研究资料,从使用情况、教学情况、研究机构等方面,对顺势疗法在南亚地区的发展进行介绍。结果:南亚地区对顺势疗法进行立法的国家有印度、巴基斯坦、孟加拉国、尼泊尔和斯里兰卡。而将顺势疗法纳入医保的只有印度和巴基斯坦。印度的顺势疗法教学机构有182所,巴基斯坦有72所,孟加拉国有23所,尼泊尔有1所。拥有单独的顺势疗法法规的国家有印度、尼泊尔、巴基斯坦;拥有顺势疗法协会的国家有印度、尼泊尔、巴基斯坦和斯里兰卡。印度对顺势疗法开展过研究。印度是南亚地区中顺势疗法发展最全面的国家,且印度各邦亦有顺势疗法的相关机构。结论:顺势疗法在南亚地区比较受欢迎,尤其是在印度和巴基斯坦,其中顺势疗法在印度的发展时间最长,体系较为完善。展开更多
基金financially supported by the National Science Foundation of China(92055205,41672223)the start-up funding from Sun Yat-sen University(74110-18841244).
文摘This paper report paleomagnetic data from late Cretaceous diorite dykes that sub-vertically intrude granodiorites in the eastern Gangdese belt near the city of Lhasa.Our research goals are to provide further constraints on pre-collisional structure of the southern margin of Asia and the onset of the India-Asia collision.Magnetite is identified as the main magnetic carrier in our study.The magnetite shows no evidence of metamorphism or alteration as determined from optical and scanning electron microscope observations.A strong mineral orientation is revealed by anisotropy of magnetic susceptibility analysis both for the intruded dykes and the country rocks.The authors interpret this AMS fabric to have formed during intrusion rather than deformation.Fifteen of 23 sites yield acceptable site mean characteristic remanences with dual polarities.A scatter analysis of the virtual geomagnetic poles suggests that the mean result adequately averaged paleosecular variation.The paleomagnetic pole from the Gangdese dykes yields a paleolatitude of 14.3°N±5.8°N for the southern margin of Asia near Lhasa.The paleolatitude corresponds to an in-between position of the Lhasa terrane during about 130‒60 Ma.Furthermore,the mean declination of the characteristic remanent magnetization reveals a significant counterclockwise rotation of 18°±9°for the sampling location since about 83 Ma.In the light of tectonic setting of the dykes,the strike of the southern margin of Asia near Lhasa is restored to trend approximately about 310°,which is compatible with the hypothesis that the southern margin of Eurasia had a quasi-linear structure prior to its collision with India.
基金supported by the Strategic Project of Science and Technology of Chinese Academy of Sciences (XDB050105003)the State Scholarship Fund of China (41272030)+1 种基金the National Basic Research Program of China (2012CB822001)IGCP608
文摘This is a new report on the early Eocene radiolarian fauna from the Sangdanlin section in the Gyirong region, along the southern margin of the Yarlung Zangbo Suture Zone. The Sangdanlin section measured in this study is divided into three lithostratigraphic units from bottom to top: the Zongzhuo, Sangdanlin, and Zheya formations. Abundant radiolarian fossils were obtained from the Sangdanlin section and 54 species of 30 genera were identified and assigned as follows: Cryptamphorella conara-C. macropora the late Cretaceous Zone and Amphis_phaera coronate, Bur)ella tetradica-Bekoma campechensis, and B.bidartensis-B. divaricata the Paleocene-early Eocene Interval Zones. The Paleocene- early Eocene radiolarian zones are comparable to the radiolarian zones RP4-RP8 in New Zealand. Based on the data of radiolaria and lithofacies, it is suggested that the Zongzhuo Formation should be deposited along the base of the north-facing, continental slope of the Greater Indian continental margin, and the Sangdanlin Formation should be a deep marine, sedimentary sequence located in a foreland basin. The early Eocene radiolarian fauna in the Sangdanlin Formation constrains the initial age of the India-Asia collision to no later than 53.6 Ma.
基金financially supported by the Strategic Priority Research Program (B type) of the Chinese Academy of Sciences (Grant No. XDB03010404)
文摘Identifying when, where, and how India and Asia collided is a prerequisite to better understand the evolution of the Himalayan-Tibetan Plateau. Whereas with essentially the same published paleomagnetic data, a large range of different India-Asia collision models have been proposed in the literature. Based upon the premise of a northwards-moving Indian plate during the Cretaceous times, we analyze the significant variations in relative paleolatitude produced by a nearly 90° counterclockwise(CCW)rotation of the plate itself during the Cretaceous. Interestingly, recent studies proposed a dual-collision process with a Greater India basin or post-Neo-Tethyan ocean for the India-Asia collision, mainly in the light of divergent Cretaceous paleolatitude differences of the Tethyan Himalaya between the observed values and expected ones computed from the apparent polar wander path of the Indian plate. However, we find that these varied paleolatitude differences are mainly resulted from a nearly 90° CCW rotation of a rigid/quasi-rigid Greater Indian plate during the Cretaceous. On the other hand, when the Indian craton and Tethyan Himalaya moved as two individual blocks rather than a united rigid/quasi-rigid Greater Indian plate before the India-Asia collision, current available Cretaceous paleomagnetic data permit only multiple paleogeographic solutions for the tectonic relationship between the Indian plate and the Tethyan Himalayan terrane. We therefore argue that the tectonic relationship between the Indian plate and the Tethyan Himalayan terrane cannot be uniquely constrained by current paleomagnetic data in the absence of sufficient geological evidence, and the so-called Greater India basin model is just one of the ideal scenarios.
基金supported by the National Natural Science Foundation of China(Grant No.41525007)the Stratigraphic Pilot Science and Technology Projects of the Chinese Academy of Sciences(Class B)(Grant No.XDB03010400)
文摘Placing precise constraints on the timing of the India-Asia continental collision is essential to understand the successive geological and geomorphological evolution of the orogenic belt as well as the uplift mechanism of the Tibetan Plateau and their effects on climate,environment and life.Based on the extensive study of the sedimentary record on both sides of the Yarlung-Zangbo suture zone in Tibet,we review here the present state of knowledge on the timing of collision onset,discuss its possible diachroneity along strike,and reconstruct the early structural and topographic evolution of the Himalayan collided range.We define continent-continent collision as the moment when the oceanic crust is completely consumed at one point where the two continental margins come into contact.We use two methods to constrain the timing of collision onset:(1) dating the provenance change from Indian to Asian recorded by deep-water turbidites near the suture zone,and(2) dating the age of unconformities on both sides of the suture zone.The first method allowed us to constrain precisely collision onset as middle Palaeocene(59±l Ma).Marine sedimentation persisted in the collisional zone for another 20-25 Ma locally in southern Tibet,and molassic-type deposition in the Indian foreland basin did not begin until another 10-15 Ma later.Available sedimentary evidence failed to firmly document any significant diachroneity of collision onset from the central Himalaya to the western Himalaya and Pakistan so far.Based on the Cenozoic stratigraphic record of the Tibetan Himalaya,four distinct stages can be identified in the early evolution of the Himalayan orogen:(1) middle Palaeocene-early Eocene earliest Eohimalayan stage(from 59 to 52 Ma):collision onset and filling of the deep-water trough along the suture zone while carbonate platform sedimentation persisted on the inner Indian margin;(2) early-middle Eocene early Eohimalayan stage(from 52 to 41 or 35 Ma):filling of intervening seaways and cessation of marine sedimentation;(3) late Eocene-Oligocene late Eohimalayan stage(from 41 to 25 Ma):huge gap in the sedimentary record both in the collision zone and in the Indian foreland;and(4) late Oligocene-early Miocene early Neohimalayan stage(from 26 to 17 Ma):rapid Himalayan growth and onset of molasse-type sedimentation in the Indian foreland basin.
文摘目的:介绍顺势疗法在南亚地区的发展现状,为我国学术界了解顺势疗法提供参考。方法:本文以History and Status of Homeopathy around the world《环球顺势疗法的历史和现状》为研究资料,从使用情况、教学情况、研究机构等方面,对顺势疗法在南亚地区的发展进行介绍。结果:南亚地区对顺势疗法进行立法的国家有印度、巴基斯坦、孟加拉国、尼泊尔和斯里兰卡。而将顺势疗法纳入医保的只有印度和巴基斯坦。印度的顺势疗法教学机构有182所,巴基斯坦有72所,孟加拉国有23所,尼泊尔有1所。拥有单独的顺势疗法法规的国家有印度、尼泊尔、巴基斯坦;拥有顺势疗法协会的国家有印度、尼泊尔、巴基斯坦和斯里兰卡。印度对顺势疗法开展过研究。印度是南亚地区中顺势疗法发展最全面的国家,且印度各邦亦有顺势疗法的相关机构。结论:顺势疗法在南亚地区比较受欢迎,尤其是在印度和巴基斯坦,其中顺势疗法在印度的发展时间最长,体系较为完善。