青藏高原整体隆升与地壳短缩增厚的物理－力学机制研究（下）

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

青藏高原整体隆升与地壳短缩增厚的物理－力学机制研究＊（下）滕吉文张中杰胡家富尹周勋刘宏宾万志超杨顶辉张秉铭张慧（中国科学院地球物理研究所）（承接本刊２卷２期１３３页）４青藏高原隆升与地壳短缩的物理－力学机制讨论青藏高原平均高度为４５００ｍ，面积达３０...

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 collisional orogeny. 2. Earthquake activities, fault plane solution and stress fields. 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 has rendered the plateau area anomalous earthquakes and stress fields, strong hydrothermal activities, rapid southward declining of Lg wave energy and strengthening of the Q value, as 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 1700km 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 model could be explained by the wedging 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 and compression, which has produced the present Himalayan collisional orogenic belt and caused the uplifting of the Qinghai Xizang Plateau.