青藏高原新生代火山活动的深部力学背景  

Deep Mechanical Background for the Cenozoic Volcanism in the Tibetan Plateau

作　　者：熊熊[1] 王继业[1] 滕吉文[2] 

机构地区：[1]中国科学院测量与地球物理研究所,湖北武汉430077 [2]中国科学院地质与地球物理研究所,北京100101

出　　处：《地球科学（中国地质大学学报）》2007年第1期1-6,共6页Earth Science-Journal of China University of Geosciences

基　　金：国家自然科学基金项目(Nos40274037;40474028);中国科学院创新方向基金项目(KZCX3-SW-153)

摘　　要：为了研究火山形成基本要素——岩浆运移通道的形成，基于重力异常反演的青藏高原下地壳底部的地幔对流应力场，结合地壳破裂形成机理和对流应力场与青藏高原新生代火山分布的关系，以及青藏高原下地幔对流演化的数值模拟结果，分析了高原火山岩浆运移通道产生的深部力学机制．研究表明，高原下地幔对流应力场存在两个大的拉张区，高原中部和北部的火山岩均分布于拉张应力区．南部的林子宗火山区对应了印度板块与欧亚大陆碰撞前或碰撞早期高原下的地幔上升流．对流应力的量级为～100Ma，这与导致地壳破裂的应力量级相当．所有这些证据表明，青藏高原下地幔对流应力场可能是导致高原地壳破裂，并发展为岩浆物质通道的主要力学机制之一．The principle prerequisite for the formation of a volcano is the generation of a channel for magma transportation. There is little research on the deep mechanical mechanism for the formation of a magma transportation channel in the Tibetan Plateau, Based on the subcrustal mantle convection-generated stress field inversed by gravity anomalies, together with its relationship to the Cenozoic volcanism in the plateau, and the mechanism of crustal fracture formation, as well as the numerical results of the evolution of mantle convection beneath the plateau, this paper investigates the deep mechanical mechanism for the formation of a magma transportation channel in the Tibetan Plateau. There are two significant extensional convectiongenerated stress zones beneath the plateau, in which the volcanic rocks in the central and northern parts of the plateau are distributed. The Linzizong volcanism in southern Tibet correlates the upwelling mantle flow prior to the India-Asla collision or during the early stage of the collision. The magnitude of the stress is -100 MPa, which is the same order of force that causes crustal fractures. The evidence implies that the mantle convection-generated stress is one of the principle causes of crustal fractures, and furthermore, the formation of the magma transportation channel in the Tibetan Plateau.

关 键 词：地幔对流 应力场 青藏高原 火山活动 岩浆通道 

分 类 号：P317[天文地球—固体地球物理学]