内蒙古苏尼特左旗地区堆晶角闪辉长岩的发现及地质意义

DISCOVERY OF CUMULUS CRYSTAL BOJITE AND ITS SIGNIFICANCE IN SONID ZUOQI AREA,INNER MONGOLIA

通过详细的野外工作和室内研究，发现苏尼特左旗附近较广泛地分布有一种主要由角闪石和外长石组成的堆晶岩，其化学成分属基性岩范畴，可定名为堆晶角闪辉长岩。这类岩体具清楚的层状构造、堆晶结构．岩石化学成分、稀土元素、结构和构造等特征均表明，该类岩石是由富水的拉斑玄武岩浆经分离结晶作用形成的，是造山带火成岩组合中的一个主要组成部分，形成于造山构造岩浆旋回的早期阶段。

There are some dark green rocks which mainly consist of plagioclase and hornblend in Sonid Zuoqi area. This kind of rock was once called dark green diorite. The results of systematic field investigation and petrological-geochemical study show that the Bor Obo pluton, which has beded structure and cumulatic texture, is cumulus crystal bojite. Its chemical composition,feature of REE, texture and structure indicate that the Bor Obo pluton is as the result of fraction crystallization of water-rich tholeiitic magma. This rock body developed during the early stage of tectonic-magma cycle, and it is an important part of igneous rock-tectonic assemblage in orogenic belt.