摘要
本文综合研究了青藏高原大地构造格局、地壳与地幔结构、地球物理场特征，对青藏高原整体隆升的物理一力学机制，进行了总结，并提出了隆升、地壳短缩和增厚的动力学模式。论文对以下五个问题进行了研究和讨论：第一，青藏高原巨厚的地壳、薄的岩石图结构、不同产状深大断裂以及推覆、切割和碰撞造山带的基本模式；第二，地震活动、断层面解与区域应力场；第三，板块运移与地体拼贴和大陆增生；第四，青藏高原隆升的物理一力学机制分析；第五，青藏高原隆升的地球动力学模式。研究结果表明，南部印度板块向北运移并与欧亚大陆板块碰撞，北部则受古亚洲板块阻隔并向南推移。在长期的碰撞与挤压作用下，造成了高原地区异常的地震活动和应力场，Ｌｇ波能量向南快速衰减和Ｑ值向南递增，水热活动强烈和地壳“南热”、“北冷”及岩石围中“壳热”、“慢冷”的格局。喜马拉雅南、北麓重力未达均衡，高山仍在上升，沿雅鲁藏布江由深部上涌的蛇绿岩套长达１７００ｋｍ，一系列走滑断层的形成和强烈的形变，形成了南界恒河平原北缘、北抵雅鲁藏布江的宽约３００～５００ｋｍ的碰撞挤压过渡带。基于此，青藏高原的隆升和地壳短缩增厚的物理一力学机制为软流圈的拖曳作用，促使印度板块与欧亚板块的碰撞和长期的挤?
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 6f 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 QinghaiXizang 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.
出处
《高校地质学报》
CAS
CSCD
1996年第2期121-133,共13页
Geological Journal of China Universities
关键词
青藏高原
整体隆升
地壳短缩
增厚
物理-力学
Qinghai-Xizang Plateau, whole uplifting, crustal shortening, collisionalcompression, low-velocity decolloment, dynamic model, physical-mechanical mechanism.
