Dissertations / Theses on the topic 'South Tibet'

Ophiolite complexes emplaced onto the Indian passive margin sequence in southwest Tibet represent the largest thrust sheet of the Neo-Tethyan oceanic crust and mantle that is preserved along the Yarlung Tsangpo Suture Zone (YTSZ). Field observations, petrological, geochemical and geochronological studies have revealed the supra-subduction zone (SSZ) type ophiolitic rocks formed in two different time frames, c. 127-124 Ma and c. ?4 Ma. The Early Cretaceous suite comprises voluminous mantle rocks, with subordinate mafic and ultramafic intrusions, while plutonic rocks are exposed locally. A shear zone complex probably representing a transform fault zone is also present. Geochemical analysis shows that the crustal rocks evolved from MORB-like to IAT to boninitic magmatism. The Late Cretaceous suite is represented by limited exposures of basaltic lavas, which have MORB-like geochemical compositions. Petrographic and geochemical evidence indicates that the majority of the mantle rocks are residues after extraction of MORB-type magma, which subsequently reacted with boninitic melts in a SSZ. Sub-ophiolite melange zones contain diverse rock types set in a serpentinte or mudstone matrix. Amongst a variety of lithologies, mid Jurassic and mid Cretaceous radiolarian cherts are exposed. Alkaline seamount volcanic rocks of inferred mid Cretaceous age were also found interbedded with cherts or overlain by limestones. Ophiolitic tholeiitic rocks were also included in the melange zones, two of which have 4°Ar_39Ar whole rock ages of c. 86 and 106 Ma. Evidence from the ophiolites and associated melange zones suggests that an intra-oceanic subduction zone initiated in the Early Cretaceous in this part of Neo-Tethyan Ocean. This SSZ system continued at least for c. 40 Ma, from the Early Cretaceous to Late Cretaceous.

The Xigaze forearc basin records the evolution of the southern Lhasa terrane convergent margin, largely affected by Neo-Tethyan subduction processes, prior to the Paleocene Tethyan Himalaya-Eurasia collision. New geologic mapping and U-Pb detrital-zircon geochronologic data from the Lazi region, 340 km southeast of Lhasa, show that forearc basin sedimentation began ca. 110 Ma conformably atop the Yarlung-Tsangpo ophiolitic melange. By this time, the arc-trench system along the southern margin of the Lhasa terrane (Eurasia) consisted of an accretionary complex, overlying ophiolitic melange, the Xigaze forearc basin, and the Gangdese magmatic arc. There is no geological evidence in the Lazi region for more than one subduction zone between the southern Lhasa terrane margin and India. Sedimentological facies analysis from Albian to Santonian clastic and carbonate sedimentary rocks preserved in the Xigaze forearc basin indicate deep-marine sedimentation characterized by hemipelagic carbonate and volcanogenic sediment-gravity-flow deposits. Sandstone modal petrographic and U-Pb detrital-zircon geochronologic data reveal Asian continental margin, Gangdese magmatic arc, and central to northern Lhasa terrane provenance. During this time, basin fill was deposited in cycles of high and low sediment flux characterized by alternating successions of clastic turbidite inner- to outer-fan deposits and hemipelagic limestone and marlstone sequences. Along-strike differences in the timing of initial forearc basin sedimentation are likely the result of intra-basin topography and/or diachronous development of ophiolitic forearc basement.

The uplift history of the Tibetan Plateau is poorly constrained in part due to its complex and extended tectonic history. This study uses basin analysis, stable isotope analysis, magnetostratigraphy, detrital zircon U-Pb dating, and paleoaltimetry, and frequency analysis to reconstruct the tectonic, spatial, and environmental evolution of the Zhada basin in southwestern Tibet since the late Miocene. The Zhada Formation, which occupies the Zhada basin and consists of ~ 850 m of fluvial, alluvial fan, eolian, and lacustrine sediments, is undeformed and lies in angular unconformity above Tethyan sedimentary sequence strata. The most negative Miocene δ¹⁸Opsw (paleo-surface water) values reconstructed from aquatic gastropods are significantly more negative than the most negative modern δ¹⁸O(sw) (surface water) values. In the absence of any known climate change which would have produced this difference, we interpret it as indicating a decrease in elevation in the catchment between the late Miocene and the present. Basin analysis indicates that the decrease in elevation was accomplished by two low-angle detachment faults which root beneath the Zhada basin and exhume mid-crustal rocks. This exhumation results from ongoing arc-parallel extension and provides accommodation for Zhada basin fill. Sequence stratigraphy shows that the basin evolved from an overfilled to an underfilled basin but that further evolution was truncated by an abrupt return to overfilled, incising conditions. This evolution is linked to progressive damming of the paleo-Sutlej River. During the underfilled portion of basin evolution, depositional environments were strongly influenced by Milancovitch cyclicity: particularly at the precession and eccentricity frequencies.

2008/2009
The area of the present study is the central part of southern Tibet. It consists of two accreted terranes, Lhasa and Himalaya terranes, which today record the deformation history that originated from the processes of collision between the Eurasia and India plates. Our study of the crust/mantle structure in terms of seismic velocity, density, anisotropy and petrologic composition are undoubtedly significant to deepen the understanding of the continent-continent collision and its dynamics. This PhD thesis can be briefly summarized into four parts that are listed in the following. 1) In order to reveal the characteristics of the crust/mantle deformation that has been generated by the Indian/Eurasia collision in the southern Tibet plateau, we study the propagation of Quasi-Love (QL) waves. Our study is based on the results from numerical modeling, which proved that QL is sensitive to lateral variation of seismic anisotropy, rather than heterogeneity and other factors. The results we obtain from processing locally observed seismograms, reveal a West-East variation of crust/mantle deformation in each terrane of the plateau. 2) A 3D density model of central-south Tibet is produced by modeling the Bouguer gravity field using all existing constraints. 3) Integrating seismic velocity and density models of the crust in the Lhasa and Himalaya terranes, we infer crustal composition models in central and southern Tibet. 4) Combining crustal density, velocity and mineralogical composition models, some important issues, such as the Indian slab subduction angle, and the relationship between crustal density and earthquake occurrences are discussed. Some results based on the gravity modeling are summarized as follows: 1) under the constraint of the geometrical structure defined by seismic data, a 3-D density model and Moho interface are proposed for central-south Tibet; 2) the lower crustal density, smaller than 3.2 g/cm3, suggests the absence of eclogite or partial eclogitization due to delamination under the central-south Tibet; 3) seismicity is strong or weak in correspondence of the most negative Bouguer gravity anomaly, so there is not a relationship between them; 4) the composition of the lower crust, determined after the temperature-pressure calibration of seismic P wave velocity, might be one or a mixture of: 1. amphibolite and greenschist facies basalt beneath the Qiangtang terrane; 2. gabbro-norite-troctolite and mafic granulite beneath the Lhasa terrane. When using the data set published by Rudnick & Fountain (1995), the composition of the middle crust turns out to be granulite facies and might be pelitic gneisses. Granulite facies used to be interpreted as residues of partial melting, which coincides with the previous study by Yang et al. (2002) on partial melting in the middle crust. Amphibolite facies are thought to be produced after delamination, when underplating works in the rebound of the lower crust and lithospheric mantle. From the seismology study, I have made the following conclusions: 1) through numerical simulation of surface wave propagation in heterogeneous media, we find that amplitude and polarization of surface wave only change a little when considering heterogeneity and QL waves, generated by surface wave scattering, are caused by lateral variation of anisotropy. 2) QL waves have been identified from the seismograms of selected paths recorded by the Tibetan station CAD, and are utilized to determine the variation of the uppermost mantle anisotropy of the Tibetan plateau. The location of the azimuthal anisotropy gradient is estimated from the group velocities of Rayleigh wave, Love wave and QL wave. We find that a predominant south-north lateral variation of azimuthal anisotropy is located in correspondence of the Tanggula mountain, and a predominant east-west lateral variation of azimuthal anisotropy is found to the north of the Gandese mountain (near 85°E longitude and 30°N latitude) and near the Jinsha river fault (near 85°E longitude and 35°N latitude).
XXI Ciclo
1981

In contrast to the oceans, deformation in the continental lithosphere is distributed over broad regions. This dissertation is composed of three separate but related studies investigating the kinematics and dynamics of such deformation. The first two studies look at the Makran subduction zone, and the third focusses on deformation in South East Tibet. The first study is an investigation of the 11 May 2013 M w 6.1 Minab earthquake which occurred at the western end of the Makran subduction zone, adjacent to the transition to continent-continent collision in the Zagros mountains. Seismological, geodetic and field results are used to study the source parameters and slip distribution of this earthquake, and demonstrate that the earthquake was left-lateral and occurred on a fault striking ENE–WSW; approximately perpendicular to previously studied faults in the adjacent Minab-Zendan-Palami fault zone. Geological and geomorphological observations of similar faults in the vicinity are used to infer that vertical-axis rotations allow a series of such faults to accommodate ∼15–19 mm/yr of N–S right-lateral shear. The dynamic implications for the transition between subduction and continental collision are discussed. The second study looks at the Makran region as a whole. First, the shape and depth of the interface with the Arabian plate is constrained by modelling the depths and mechanisms of earthquakes across the region, and combining these with additional seismological constraints. These constraints on the subduction interface are used to investigate elastic strain accumulation on the megathrust in the western Makran, which has important implications for seismic and tsunami hazard in the region. Second, the kinematics at the northern edge of the Makran accretionary prism are investigated using a combination of geodetic and geomorphological observations, addressing the long-standing tectonic problem of how the right-lateral shear taken up by strike-slip faulting in the Sistan Suture Zone in eastern Iran is accommodated at the zone’s southern end. Finally, the kinematics and dynamics of the accretionary prism are investigated. By considering the kinematics of the 2013 Balochistan and Minab earthquakes, local gravitational and far-field compressive forces in the Makran accretionary prism are inferred to be balanced. This force balance allows the mean shear stress and effective coefficient of friction on the Makran megathrust to be calculated, 5–35 MPa and 0.01–0.03 respectively. The final part of this thesis focusses on the temporal evolution of topography in South East Tibet. Recently published paleoaltimetry results based on stable-isotope geochemistry are used to provide constraints on vertical motions. These demonstrate that uplift is much slower than had previously been suggested from thermochronometric data. Numerical modelling of the time evolution of a gravitationally-driven fluid is used to investigate the effect of lateral rheological contrasts on the shape and evolution of topography. In such a flow, material at the surface can be transported hundreds of kilometres, an effect which should be accounted for in paleoaltimetric analysis. Lateral rheological contrasts, analogous to the relatively undeforming Sichuan Basin and Central Lowlands of Myanmar, can reproduce the main features of the present-day topography, GPS velocity field and earthquake-derived strain rate without the need for a low-viscosity lower-crustal channel.

In this thesis, I explore the use of copulas in non-copula constructions in the languages of South Asia to establish possible genetic and areal tendencies in the distribution. Using materials – language descriptions and data – from Grierson’s Linguistic Survey of India, I examine the phenomenon in 206 languages from four families (Munda, Dravidian, Indo-Aryan and Sino-Tibetan). It is found that the languages of South Asia appear to be more likely than the world-wide average to use the copula in non-copula constructions and that at least Munda, Dravidian and Indo-Aryan use it in the same way with regards to tense, namely in the past and present but not the future. Finally, I argue that there is some evidence supporting that the use of the copula in non-copula constructions is an areal feature, though more work is needed to make any definitive conclusions.

碩士
國立臺灣大學
地質學系
85
Systematic fission-track dating analysis on the minerals extracted from Gangdese batholiths, South Tibet have been carried out in this study. The preliminary FTD result shows that the granitic basement had not uplifted to the surface level until early-Miocene. According to FTD dates of apaites, which exhibit lower closure temperature (ca. 90~110oC) and could be able to indicate the last stage thermal record of the basement, diachronous uplift of Tibetan plateau occurred, at least in Lhasa block, during earl to middle- Miocene age.

碩士
國防大學
戰略研究所
96
Across the roof of the world to South Asia is one grand strategy of China in 21st century. Under the premise of national interests, and the priority of “great power as key, periphery as first”, China has adopted active effort to reach its South-West geostrategy. The construction and opening of Qinghai Tibet Railroad is not only a part of China’s Great Western Development Strategy, but also an important infrastructure of Tibet’s development and an indicative project of Western Development Strategy. Western Development Strategy is an important policy of regional economic development in national security strategy of China. The opening of Qinghai Tibet Railroad leads to inspire China’s political, economic, and military activities. Besides, the railroad can penetrate strategic array to South Asia, enlarge its sphere of influence of Euro-Asia area, infect the development of stable relationship with peripheral nations, change the sphere of influence of South-West geostrategy. In short-term, though the extremly high expense of constructing Qinghai Tibet Railroad can not fit economic benefits, the goals that China has insisted in the construction are mainly to promote economic and touristic interests, and to examine her efforts to seek South Asia strategic goals. The strategic implications of the construction of Qinghai Tibet Railroad involve multidimensional and profound significance. They have demonstrated that political considerations is priority, military power serves as pillar, economic development as attempt, that is, to maintain political stability by means of economy. China’s future policy will be good-neighborhood-oriented. Starting with peaceful cooperation to get regional equilibrium, which will facilitate the contest focal point of South-East Asia and North-East Asia. In long-term, active defence will be the supreme guideline, to defense as offense, to offense with defence, soft power(economy, culture, technology) as pioneer, hard power(military power) as shield to foster itself, thus enhance the comprehensive national power of China.

碩士
中興大學
國際政治研究所
95
Qinghai-Tibet railroad, the infrastructure of Big Development in west China, is officially open to traffic on July 1, 2006. Hu Jintao, General Secretary of Chinese Communist Party, personally went to cut the ribbon in the ceremony for opening to traffic in Golmud city, Qinghai Province. Hu indicated that, "The Qinghai-Tibet railroad regarding two provincial capital areas speeds up the development of economic society, improves life of various races group, promotes the national unity and consolidates motherland border defense, all has the great significance." After the Qinghai-Tibet railroad being finished and open to traffic, it has the certain influence and the function regarding overall strategy of Chinese Communist Party in the South-Asia. Regardless of in politics, economy, international, military, and even in the frontier question all has the in-depth strategic meaning. In political strategy, the Chinese Communist Party declared the Qinghai-Tibet railroad is the great engineering achievement, internally by which they can control Tibet and extinguish the Tibetan independence; and so on, foreignly they can moderately solve territory question between China and India. In economical strategy, internally the railroad may encourage the development of Tibet economy, accelerate traveling market for connecting Tibet to Mainland and form the ring-like traveling line in west China; foreignly base on the superiority for close border to the Middle East, the central Asia oil source, petroleum can be transported to Pakistan by the oil tube or tanker, then again through the road, railroad petroleum can be imported to Tibet, thus avoids through the dangerous Melaka channel. In military strategy, internally they may consolidate the security of west border area, perfect the transportation network of army; foreignly, they may break through blockade by US. Along with the Chinese economy rapid development, China is important in international scene status day by day, "China rises" is the topic which now the international society most pays attention. But also as a result of China''s economical development, specially in Chinese Communist Party''s military expenses expenditure fast growth, "the Chinese Communist Party threat theory" also becomes the focal point which the west pays attention day by day. Qinghai-Tibet railroad being open to transport, the biggest difference lies in the Chinese Communist Party be able to deliver the military force to the south-west area in the shortest time by inland transportation, therefore, the Big Development in west China will bring to the South Asia area may be the threat or prospers, respectively various countries in the South Asia have the different opinion. In light of the whole, the Qinghai-Tibet railroad being finished and open to traffic, is advantageous to the Chinese Communist Party, she promotes the whole the strategic layout, and have the multiplication function for the "rises".

Understanding the development of the Himalaya is critical to elucidating continental collisional processes. The Greater Himalayan sequence (GHS), the exhumed mid-crust of the Himalayan orogen, records the tectonometamorphic evolution of the Himalaya from its deep hinterland to its foreland. The GHS in central Nepal and adjacent Tibet is deformed pervasively; quartz c-axis orientation fabrics from across the GHS indicate that it was deformed at high temperatures (~550-650˚C). The asymmetries of these quartz c-axis fabrics confirm field observations that define a reversal in shear sense from top-south shear near the bottom and middle of the GHS to top-north shear near the top of the package proximal to the South Tibetan detachment system (STDS). Estimates of mean kinematic vorticity from across the GHS indicate a pure shear contribution between 33% and 67%. U-Pb geochronologic data from the upper GHS exposed in the Changgo culmination in south Tibet indicate that melt crystallization and metamorphism related to crustal thickening occurred at ca. 35 Ma and was succeeded by a second metamorphic episode and syn-kinematic voluminous anatexis at ca. 22 Ma. The upper GHS was thinned vertically by 50% and extended horizontally during and immediately after the second metamorphic event, in a manner typical of the deep hinterland regions of orogens. In central Nepal, the ductile lateral extrusion of the upper GHS between the Main Central thrust (MCT) below and STDS above ceased by ~19 Ma. The cessation of lateral extrusion followed the collapse of the orogenic wedge and a reduction in the gravitational potential necessary to drive the propagation of deformation southwards towards the foreland. To restore the geometry of the wedge, deformation stepped out-of-sequence into southern Tibet, with the exhumation of the Changgo culmination and the North Himalayan antiform, before migrating incrementally back toward the foreland. Subsequently, the MCT migrated downward structurally adding material to the lower GHS as thrust slices, characteristic of foreland-style deformation. Thus, the transition between the upper and lower GHS in central Nepal records the transition from hinterland-style deformation to foreland-style deformation.
Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2009-04-13 11:48:45.702

abstract: Since 1998 and as recently as November 2018, 165 Tibetans have burned themselves alive in public protest, both inside Tibet and in exile. This study foregrounds Tibetan refugees’ interpretations of the self-immolation protests and examines how the exile community has socially, politically, and emotionally interrogated and assimilated this resistance movement. Based upon eleven months of ethnographic field research and 150 hours of formal interviews with different groups of Tibetan refugees in northern India, including: freedom activists, former political prisoners, members of the exile parliament, teachers of Tibetan Buddhism, families of self-immolators, and survivors of self-immolation, this project asks: What does activism look like in a time of martyrdom? What are the practices of solidarity with the dead? How does a refugee community that has been in exile for over three generations make sense of a wave of death occurring in a homeland most cannot access? Does the tactic of self-immolation challenge Tibetan held conceptions of resistance and the conceived relationship between politics, religion and nation? These questions are examined with attention to the sociopolitical expectations and vulnerabilities that the refugee community face. This study thus analyzes what it means to mourn those one never knew, and examines the fractious connections between resistance, solidarity, trauma, representation, political exigency, and community cohesion. By examining the uncomfortable affect around self-immolation, its memorialization and representation, the author argues that self-immolation is a relational act that creates and ushers forth witnesses. As such, one must analyze the obligations of witnessing, the barriers to witnessing, and the expectations of solidarity. This project offers the theory of exigent solidarity, whereby solidarity is understood as a contested space, borne of expectation, pressure, and responsibility, with its expression complex and its execution seemingly impossible. It calls for attention to the affective labor of solidarity in a time of ongoing martyrdom, and demonstrates that in the need to maintain solidarity and social cohesion, a sense of mutual-becoming occurs whereby the community is reconciled uneasily into a shared fate.
Dissertation/Thesis
Doctoral Dissertation Justice Studies 2019