沱沱河地区埃达克岩的发现及意义

在青藏高原平均海拔4000m以上的沱沱河地区,发育了一套新生代始新世特殊的侵入体.依据岩石组合系列和地球化学特征,将其划分为灰白色闪长玢岩和灰白色石英闪长玢岩两种侵入岩,由13个侵入体组成,出露总面积为26.85km2.这些岩石具有高铝、高锶而贫重稀土的特征,与区域上其他时代、类型的侵入岩形成显明对比.这套岩石组合的特征与埃达克岩的特征一致,却与典型的埃达克岩形成环境又不同,其为挤压消减环境,值得关注.笔者重点探讨这套新生代埃达克岩的岩石学、地球化学特征及形成时代和环境分析,以及对区域地质研究的重大意义.

Discovery and Geological Significance of Adakites in the Tuotuo River Region

A suite of Cenozoic intrusive rocks is exposed in the Tuotuo river region in Qinghai-Tibet plateau. According to the rock assemblage and geochemical characteristics, the rocks can be divided into two sorts of intrusives : quartz-diorite-porphyrite and diorite-porphyrite. The suite is made up of 13 intrusive bodies in an area of 26.85 km2. These rocks are high in Al and Sr, and low in heavy REE. The features are identical to those of adakites. However, their formation environment of compression and subduction is different from the ideal adakites.This is noteworthy of further concern. The article primarily discusses petrologicaland geochemical features, formation ages and environment of the Cenozoic adakite-like intrusive rocks, and also their geological significance for regional geology.