三江地区义敦岛弧碰撞造山过程：花岗岩记录

义敦岛弧碰撞造山带是特提斯－喜马拉雅巨型造山带中的一个复合造山带。本文利用义敦岛弧碰撞造山带29个花岗岩体的43件同位素测年数据，结合岩石地球化学特征，建立了造山带花岗岩的时间坐标。初步识别出4套不同成因类型的花岗岩，即印支期弧花岗岩、燕山早期同碰撞花岗岩、燕山晚期A型花岗岩和喜马拉雅期花岗岩。据此，再造了造山带的形成过程与演化历史：印支期的大规模俯冲造山作用（238－210Ma)，形成义敦火山岩浆弧；大约自206Ma始，发生弧－陆碰撞，伴随岛弧地壳挤压收缩和剪切变形，发育同碰撞花岗岩；进入燕山晚期（138－73Ma)，岛弧碰撞造山带发生造山后伸展作用，形成A型花岗岩带；喜马拉雅期发生陆内造山作用（65－15Ma)，岛弧碰撞造山带出现逆冲－推覆和大规模走滑平移，伴随喜马拉雅期花岗岩的侵位和拉分盆地的形成。

Collision-Orogenic Processes of the Yidun Arc in the Sanjiang Region: Record of Granites

The Yidun arc collision-orogenic belt is a composue orogenic belt of the giant Tethys-Himalaya orogenic zone. Based on 43 isotopic ages of 29 granite bodies in combination of their petro-geochemistries, the paper established a time coordinate for the granites of the orogenic belt. Four genetic types of the granites were identified as follows: Indosinian arc granites, early Yanshanian syn-collision granites, late Yanshanian A-type granites and Himalayan intra-continental granites. The formation and evolution were reconstructed. A large-scale Indosinian subduction-orogenesis led to the formation of the Yidun magmatic arc (238-210 Ma). From about 206 Ma there occurred arc-continent collision accompanied by compressional contraction and shearing deformation of the arc crust and development of syn-collision granites. In the late Yanshanian epoch (138-73 Ma) post-orogenic extension came into action and resulted in the generation of A-type granites. During the Himalayan (65-15 Ma) intra-continental orogenic movement a large-scale strike-slip thrusting induced the intrusion of granites and development of pull-apart basins.