西藏班公湖蛇绿混杂岩带演化特征

On evolution characteristics of admixture ophiolite belt in Bangong Lake of Tibet

蛇绿岩带是大陆造山带中残存的古大洋岩石圈和上地幔的残片,它记录了洋壳地幔的对流、变形、熔融以及交代过程;蛇绿混杂岩带是不同时代、不同大小、不同构造环境的沉积物及洋壳和上地幔的残片,经俯冲消减、碰撞后混杂堆积构成的无序组合带,它涵盖了洋盆形成、俯冲消亡、弧-弧或弧-陆碰撞到陆内汇聚的造山作用时空演化全过程。从班公湖蛇绿岩带内部结构、岩石学特征、地球化学特征等方面进行了详细的野外调查和研究,最后从地质构造、地球化学及区域对比3个方面,分析了班公湖蛇绿岩的形成环境。

Ophiolite belt records the process of oceanic crust＇s convection,deformation and melting and replacement which was the remnant of the ancient oceanic lithosphere and the fragments of the upper mantle.It was the pieces of upper mantle and sediment formed in different time,with varied size and different tectonic environment,the disordered combination band through colliding,subduction and piling up,covering the whole temporal and spatial process of ocean basin formation,subduction,and arc-arc or arc-continent collision to the intra-continental orogenesis.Ophiolite was the main source of information,which knew the evolution of original oceanic lithosphere tectonic system,also was the window of the department of island-arc basin.The authors carried out a detailed field survey and research form internal structure,rock characteristics and geochemistry of admixture ophiolite belt in Bangong Lake,analyzed the formation environment of Bangong Lake ophiolite in the fields of geological structure,geochemistry and regional comparison.