雅鲁藏布江蛇绿岩的侵位机制:一个新的分析模型

蛇绿岩侵位机制是板块构造理论中一直没有得到合理阐释的科学问题,制约了许多次级问题的解决。本文综述了已发表的关键资料和地质观察,提出了一个新的分析模型。蛇绿岩带的长距离延伸表明其形成过程与板块汇聚过程紧密相关;冈底斯岩浆弧的两期弧岩浆活动暗示汇聚板块边缘的构造性质曾经发生过转换;前人报道的玻安岩缺乏充分的地质学、岩石学和矿物学约束;强还原晶体群的普遍性暗示蛇绿岩侵位过程与大规模流体活动有关。据此,本文提出了一个由流体协助的蛇绿岩侵位模型,认为俯冲板块回卷、断离、流体-岩石圈相互作用、大洋岩石圈穹隆等过程是蛇绿岩侵位的基本控制因素。

The emplacement of the Yarlung Zangbo ophiolites:A new analytical model

The emplacement mechanism of ophiolites is a scientific problem in the plate tectonics which has not been clearly explained till now, and such a situation restricts resolving many secondary questions. In this paper, a new analytical model is proposed on the basis of combination of the key published data and the field observations. The large length of the ophiolite belt suggests a close relation between its formation and the converging plate process; the two phases of arc magmatism in the Gandise magmatic arc indicate translation of the tectonic features at the converging plate edges; there are not sufficient geological, petrological and mineralogical constraints in the previous reports about boninite; the universal discovery of the strongly reduced crystal populations suggests that the obduction process of ophiolite was related to the large scale activity of the deep fluids. Accordingly, a new model of ophiolite emplacement is proposed and called fluid-assisting model, in which the processes such as rollback and break-off of the subducted plate, fluid-lithosphere interaction, and oceanic lithosphere dome seem to have been the essential factors controlling ophiolite emplacement.