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PHYSICAL-MECHANICAL MECHANISM FOR THE WHOLE UPLIFTING OF THE QINGHAI-XIZANG PLATEAU AND THE LATERAL SHORTENING AND VERTICAL THICKENING OF THE CRUST

Teng Jiwen, hang Zhongjie, Hu Jiafu, Yin Zhouxun, Liu Hongbin, Wan Zhichao, Yang Dinghui, Zhang Bingming and Zhang Hui   

  1. Institute of Geophysics, Chinese Academy of Science, Beijing, 100101
  • Received:1996-06-20 Revised:1996-06-20 Online:1996-06-20 Published:1996-06-20

Abstract: The Himalayan movement is the latest strong movement of the crust and the most important geological event in Asia during the Mesozoic and Cenozoic Eras. This movement. which has built up the Himalayan Mountains and is still in progress. affects a wide area of eastern Aisa and is regarded as the cause for whole uplifting of the Qinghai Xizang Plateau. A variety of hypotheses have been suggested for This uplifting mechanism, but none of them is convincible. In order to investigate the physical-mechanical mechanism for the whole establish and to establish a geodynamic model for crustal shortening and thickening, this paper, starting from discussions on the Tectonic framework. crust and mantle structure and geophysical field, will be concentrated on the following five problems: 1. The basic models for the formation of thick crust. thin lithosphere, deep faults of varying features and for thrusting. intersecting and collisions orogeny. 2. Earthquake activities, fault plane solution and stress field 3. Plate movement. terrain amalgamation and continental accretion. 4. Physical-mechanical mechanism for uplifting of the Qinghai-Xizang Plateau. 5. Geodynamic model for the uplifting. As a result of the northward movement of the India plate and its collision with The Eurasia continent, the long term Tectonic compression ruts rendered the plateau area anomalous earthquakes and stress fields, strong hydrotherrnal activities, rapid southward declining of Lg wave energy and strengthening of the Q value. a well as the pattern of southward increasing of crustal temperature and “hot”crust relative to “cold” mantle in the lithosphere. Gravity isostasy has not yet been reached at both south and north piedmonts. and high mountains have been continuously uprising. The ophiolite suite emplaced along the Yaluzangbu River extends 1 700km in length. A series of strike-slip faults were formed and rocks were strongly deformed. A transitional zone, 300 to 500km in width between the north margin of the Ganges Plain and the Yaluzangbu River, has been developed by collisional compression. All these facts appear to indicate that the physical mechanical mechanism for the uplifting of the Qinghai-Xizang Plateau and the shortening and thickening of the crust could be understood in terms of the asthenosphere dragging and the consequent long-term collision and compression between the India and Asia Plates. The dynamic mode1 could be explained by theⅥ edging of crustal materials from India plate into that under the Qinghai-Xizang Plateau along the low velocity zones in the middle part of the crust during collision anticompression, which has produced the present Himalayan collisional orogenic belt and caused the uplifting of the Qinghai Xizang Plateau.