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1.
Variations of stable isotopic compositions in precipitation on the Tibetan Plateau and its adjacent regions 总被引：15，自引：3，他引：15
There is no temperature effect in the southern Tibetan Plateau and South Asia to the south of the Tanggula Mountains. Amount
effect has been observed at a few sampling stations accounting for about a half of the statistical stations. There is notable
temperature effect in the middle and northern Tibetan Plateau and its adjacent Central Asia to the north of the Tanggula Mountains.
Because vapor directly originates from low-latitude oceans, the relative heavy δ18O with small variation characterizes the rainfall in South Asia. A sharp depletion of the stable isotopic compositions in
precipitation takes place from Kyangjin on the southern slope of the Himalayas to the Tanggula Mountains in the middle plateau.
From the Tanggula Mountains to the northern Tibetan Plateau, the δ18O in precipitation increases with increasing latitude. 相似文献
2.
As a result of the left-lateral strike-slipping of the Altyn Tagh fault in Neotectonic period, a contra-rotational structure, namely the Zhaobishan vortex structure, has developed at the juncture of the main Altyn Tagh fault and the northern fringe fault of the Qilian Mountains.Preliminary analysis on the deformation and evolution of the Zhaobishan vortex structure. In combination with the previous data, suggests that the tectonic transform between the Altyn Tagh fault and the northern fringe fault of the Qilian Mountains attributes to the deformation of the rotational structure. The existence of a series of rotational structures along the Altyn Tagh fault and on the northeastern edge of the Qinghai-Xizang(Tibet) plateau indicate that as the substance in the northern Qinghal-Xizang (Tibet) plateau moves clockwise around the eastern tectonic knot of the Himalayas, rotational structures become the principal mode on the northern marginal zone of the Plateau of transforming and absorbing tectonic deformation. 相似文献
3.
Abstract Since 1973 new data have been obtained on the maximum extent of glaciation in High Asia. Evidence for an ice sheet covering Tibet during the last glacial period means a radical rethinking about glaciation in the northern hemisphere. The ice sheet's subtropical latitude, vast size (2.4 million km2 ) and high elevation (6000 m a.s.l.) are supposed to have resulted in a substantial, albedo-induced cooling of the Earth's atmosphere and the disruption of summer monsoon circulation. Moraines were found to reach down to 460 m a.s.l. on the southern flank of the Himalayas and to 2300 m a.s.l. on the northern slope of the Tibetan Plateau, in the Qilian Shan region. On the northern slopes of the Karakoram, Aghil and Kuen-Lun Mountains, moraines occur as far down as 1900 m a.s.l. In southern Tibet, radiographic analyses of erratics suggest a former ice thickness of at least 1200 m. Glacial polish and roches moutonnées in the Himalayas and Karakoram suggest former glaciers as thick as 1200–2700 m. On the basis of this evidence, a 1100–1600-m lower equilibrium line has been reconstructed, resulting in an ice sheet of 2.4 million km2 , covering almost all of Tibet. Radiometric ages, obtained by different methods, classify this glaciation as isotope stage 3–2 in age (Würmian, the last glacial period, ca 60 000–18 000 years ago). 相似文献
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Introduction Major tectonic activities occur in collisions zones between plates or intra-plate continental blocks. Therefore, it is significant to investigate collision processes. We know that orogenic and seismic belts in plate margins are closely relate… 相似文献
6.
跨越中、印、缅三国交界的喜马拉雅“东构造结”地区（92°E～97°E，26°N～30°N）有一半以上的面积尚没有重力测点，是重力数据空白区,故无法直接研究其重力场特征与深部地壳结构（构造）.本文应用卫星重力异常资料作为近似空间重力异常，经计算给出的布格重力异常，其特征与该地区的地形高程呈很好的镜像相关.据此得到该区不同方位的3个地壳深部结构剖面.重力异常反演求得青藏高原地壳厚度>70 km；喜马拉雅造山带为55 km左右；布拉马普特拉河谷盆地为33～35 km；那加山山脉地区为40～45 km，即呈现出3个不同构造单元的展布.同时求得“东构造结"区由高密度的刚性物质构成，在印度洋板块的碰撞、挤压作用下呈向北运移，并插入青藏高原东缘.基于这样的构造格局和深层动力过程，导致了青藏高原东南缘和东北缘的强烈构造运动，大、小地震的频频发生和矿产资源的聚集. 相似文献
7.
Variation of Shear-wave Residuals and Splitting Parameters from Array Observations in Southern Tibet 总被引：1，自引：0，他引：1
—A tight array of seismographs spanning a 500 km traverse of southern Tibet resolved anisotropy from SKS with a spatial variation of its direction and an increase northward of the splitting delay, as well as of its first arrival residual. Both waves split by velocity anisotropy are slow relative to P and their waveform analysis may be interpreted to suggest attenuation anisotropy. The array here provides examples of residuals and splitting of other S waves which do not tightly conform to the anisotropy assumed in the simplest model of olivine of transverse isotropy with horizontal symmetry axis. S waves are also split, with parameters which vary along the array, and hence are relevant to near-receiver structure like those of SKS. Their splitting delay, for non-vertical incidence and polarization, appears larger than that for SKS. Residuals of S-wave first arrivals and splitting delays increase less northwards for S than SKS. Anisotropy with a slow vertical axis may account for these observations. Its origin may be related to horizontal shear or flow in low-velocity layers. 相似文献
8.
QuanLian Li NingLian Wang XiaoBo Wu JianChen Pu JianQiao He Jun Xie 《中国科学D辑(英文版)》2009,52(11):1803-1812
We report on the concentration and compositional features of n-alkanes of natural and anthropogenic origins in the snow samples collected from the Qiyi glacier in the Qilian Mountains,
the Yuzhufeng glacier in eastern Kunlun Mountains, the Xiaodongkemadi glacier in the Tanggula Mountains, and the Gurenhekou
glacier in the Nyainqêntanglha Range. The results indicate a decrease in the total n-alkane concentration (T-HCs) from the northeast to the south over the Tibetan Plateau. The T-HCs in these studied areas were
close to those in the Belukha and Sofiyskiy glacier, Russian Alati Mountains and the Dasuopu glacier in the Himalaya but were
much higher than those in the Greenland ice sheet, suggesting that the mountain glaciers in the Asian continent may receive
a higher loading of n-alkanes than the Greenland ice core. Moreover, the compositional characteristics of n-alkanes indicated that the n-alkanes in the studied areas were probably originated from the plant waxes as well as the fossil-fuel combustion exhaust,
whereas the contribution from the lower organisms was small. In addition, the plant wax (Cn(wax)) and anthropogenic (non-Cn(wax)) contributions revealed that fast industrialization may have significant effects on the organic pollutant composition
in glacier over the Tibetan Plateau and its circumference environment. Particularly, except for the Yuzhufeng glacier, the
ΣnC21
−/ΣnC22
+ and (nC15+nC17+nC19)/(nC27+nC29+nC31) ratio decreased from the Qiyi glacier to the Gurenhekou glacier over the Tibetan Plateau, while the carbon preference index
(CPI) values increased. These results indicate a decrease in terrigenous input while an increase in marine input from the
northeast to the south over the Tibetan Plateau. These two ratios can be used as the climatic and environmental change indicators. 相似文献
9.
Umesh Chandra 《Physics of the Earth and Planetary Interiors》1979,20(1):33-41
Three basic tectonic units, the Eurasian continent, the Rigid Boundary Zone and the Indian continent, are recognized. The Rigid Boundary Zone is identified with aseismic lineaments on an epicenter map of the Himalayas and their vicinity. The origin of the Himalayan syntaxes, their re-entrant character, and the observation that most of the Himalayas are made up of rocks belonging geologically to the Indian peninsular shield, are explained by deformation of the Indian continent within this Rigid Boundary Zone since the continental collision. The focal mechanism solutions of six earthquakes in the Indian Peninsula support the inference derived from the model that the high stresses generated by the continental collision may be very extensive spatially, and that the entire Indian Peninsula may be under a state of left lateral shear along NNE vertical planes. 相似文献
10.
用布置在亚东—格尔木的164个流动地震台站记录的926个远震事件的24241条射线,进行远震P波层析成像处理,高分辨率的西藏高原上地幔的速度结构图,显示了印度巨厚地幔岩石圈在向高原之下推进的过程中,在高喜马拉雅之下拆分成上、下两层,这是发生的第一次拆沉. 下层从高喜马拉雅以下约以22°的角度向高原北部插入到350km 深;而其上层则向北伸展直到雁石坪,并构成了高原薄的地幔岩石圈. 在雁石坪北（33.7°N）,当其与亚洲大陆岩石圈地幔相遇后发生断离并下沉. 再次证实了五道梁（35.27°N）深部低速体的存在,本区内地壳内低速物质可能与上述运动有联系,反映了深层热物质的上涌. 相似文献
11.
Chang Li Robert D. van der Hilst M. Nafi Toksöz 《Physics of the Earth and Planetary Interiors》2006,154(2):180-195
We have produced a P-wave model of the upper mantle beneath Southeast (SE) Asia from reprocessed short period International Seismological Centre (ISC) P and pP data, short period P data of the Annual Bulletin of Chinese Earthquakes (ABCE), and long period PP-P data. We used 3D sensitivity kernels to combine the datasets, and mantle structure was parameterized with an irregular grid. In the best-sampled region our data resolve structure on scale lengths less than 150 km. The smearing of crustal anomalies to larger depths is reduced by a crustal correction using an a priori 3D model. Our tomographic inversions reveal high-velocity roots beneath the Archean Ordos Plateau, the Sichuan Basin, and other continental blocks in SE Asia. Beneath the Himalayan Block we detect high seismic velocities, which we associate with subduction of Indian lithospheric mantle. This structure is visible above the 410 km discontinuity and may not connect to the remnant of the Neo-Tethys oceanic slab in the lower mantle. Our images suggest that only the southwestern part of the Tibetan plateau is underlain by Indian lithosphere and, thus, that the upper mantle beneath northeastern Tibet is primarily of Asian origin. Our imaging also reveals a large-scale high-velocity structure in the transition zone beneath the Yangtze Craton, which could have been produced in multiple subduction episodes. The low P-wave velocities beneath the Hainan Island are most prominent in the upper mantle and transition zone; they may represent counter flow from the surrounding subduction zones, and may not be unrelated to processes beneath eastern Tibet. 相似文献
12.
观测的证据充分表明,印度——欧亚的缝合带雅鲁藏布江上存在自南向北的地壳俯冲带,它穿过莫霍面,深度大约达到100 km. 喜马拉雅中可能存在多重的地壳俯冲. 它们有别于海洋碰撞时所产生的整个岩石圈俯冲. 作者观测到雅鲁藏布江以北上地幔的板片构造,它可以解释为印度向欧亚俯冲时上地幔岩石圈的痕迹. 它们说明与洋——陆的俯冲不同,印度向欧亚俯冲时,地壳与上地幔岩石圈出现拆层现象. 综合现有的地壳上地幔构造,显示在不同地质年代中,印度与欧亚之间产生自南向北以及自北向南相反方向的俯冲,而且俯冲带周围出现某些速度异常区. 相似文献
13.
Ample observational evidence shows that there is a northward crustal subduction zone underneath the Yarlung Zangbo suture between India and Eurasia. It penetrates Moho to a depth of about 100 km. There are probably multiple such crustal subductions under the Himalayas. They are different from lithosphere subduction during oceanic collisions. The detected slabs in the upper mantle north of the Yarlung Zangbo suture can be interpreted as remains of the Indian Plate’s mantle lithosphere. In contrary to ocean-continent subduction, the mantle lithosphere is delaminated from the crust as the Indian Plate subducts underneath Eurasia. Existing structural images of the crust and upper mantle of the Tibetan Plateau reveal that there were both northward and southward subductions over different geological periods, causing some seismic velocity anomalies around those subduction zones. 相似文献
14.
Barbara Romanowicz 《Physics of the Earth and Planetary Interiors》1984,36(2):116-123
A method is presented to derive pure path attenuation coefficients of Rayleigh waves, in the period range 30–90 s, across the Tibet Plateau, using events located within Tibet and observed at teleseismic distances. This method uses data from 2 events and 2 stations simultaneously, these being aligned along a great circle path, and, for relatively small events, is practically free of errors due to inaccurate knowledge of the source radiation patterns.In spite of large standard errors due to the impossibility of separating effects of anclasticity from spurious effects on amplitudes such as scattering or multipathing, results seem to indicate an anelastic model of the crust and upper mantle compatible with shear velocity models derived independently, with a thick crust and in particular, a thick high Q lid and thin low Q zone consistent with a shield like upper mantle beneath Tibet. 相似文献
15.
Han-Shou Liu 《Physics of the Earth and Planetary Interiors》1985,40(1):43-60
This paper uses plate tectonics and satellite-derived gravity data to further discussion of crustal deformation under the Tibetan Plateau. The first of our three contributions is a spherical harmonic analysis of the global plate boundary system. A distribution of 470 Dirac delta functions is applied to describe the generating forces according to the rates of crustal creation and destruction on the plate boundaries. Analysis of the extensional and compressional forces in the spreading and subducting zones shows that the present global plate motion causes compressional stresses in the N-S direction under the Tibetan Plateau. The second contribution is the calculation of the crustal stresses in Tibet as inferred from satellite gravity data. By applying solutions to the problem of the spherical shells, the satellite-determined stresses indicate that the up-welling mantle material under Tibet induce N-S and E-W extension. Finally, a superimposed stress system is constructed. This stress system shows that the present crustal deformation in Tibet does not produce N-S shortening but generates E-W extension.The results of this paper have provided geodynamical explanations for geological field observations in Tibet and fault plane solutions of earthquakes in the Tibetan side of the India-Eurasia collision. The stress patterns reveal that the cold downwelling mantle convection flow beneath southern Tibet pulls the Indian plate down but applies a bending moment on the end of the plate to uplift and support the mass of the Himalayas. 相似文献
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The surface uplift history of the Tibetan Plateau has provided a key boundary criterion for various geological, climatic, and environmental events since the Cenozoic. The paleoelevation history of the plateau is organically associated with interactions amongst deep geodynamics, earth surface processes, and climate change. Understanding of plateau uplift history has been advanced by the development of a number of paleoaltimetries and their application to studies of the Tibetan Plateau: the paleogeomorphic scenario for the Early Eocene Tibetan Plateau is thought to include two high mountains, the ca. 4500 m Gangdese Mountains to the south, and the ca. 5000 m Qiangtang Center Watershed Mountains to the north. Between these ranges, a low-elevation basin (ca. 2500 m) is thought to have been present. The Himalayas in the southern Tibetan Plateau was close to sea level at this time, while the Hoh Xil Basin in the north reached an elevation of no more than 1500 m. Thus, the so-called “Roof of the World” Tibetan Plateau formed subsequent to the Miocene. Nevertheless,, the uplift histories of the different terranes that comprise this plateau currently remain unclear, which constrains the uplift history reconstruction of the entire Tibetan Plateau. Additional paleoelevation data from different areas, obtained using multi-paleoaltimeters, is required to resolve the forms and processes of Tibetan Plateau uplift and extension. 相似文献
18.
Climate change and sediment flux from the Roof of the World 总被引：2，自引：0，他引：2
Potential rises in global temperature are likely to have major impacts on high altitude environments, including glacier recession and permafrost degradation. In turn, these could have far‐reaching impacts on riverine sediment flux. Such impacts are emerging in the Himalayas and Tibet Plateau region, one of the world's largest and most environmentally‐sensitive cold regions. Closer monitoring is urgently required to track changing trends of sediment load from the interactions of glacial recession treat, rainfall changes and human interventions, and to study the implications of such changes for the large Asian river systems of the region. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Modern tectonic stress field in the Chinese mainland inverted from focal mechanism solutions 总被引：1，自引：0，他引：1
IntroductionTheinversionapproachofregionalstressfielddevelopedinrecent10to20yearsprovidesausefultoolforstudyingthemeanstressinagivenregion(Angeller,1979;Ellsworth,1981,Xu,Ge,1984).Becauseitusesmultitudinousfaultsinsteadofsinglefault,itcanremovetheinhomogeneityoflocalmediumsoastorevealtheregionalstressinformation.Besides,thismethodproducesaRvalue,whichisdefinedby(O-2--q)/(q--q),andmaydescribestherelativemagnitUdeofintermediateprincipalstress,whereq,acand%arethemaximum,theintermediateandthemi… 相似文献