青海省德尔尼蛇绿岩的地球化学特征及其大地构造意义

Geochemistry of Derni ophiolite and its tectonic significance.

德尔尼蛇绿岩位于青海省东南部玛沁地区 ,蛇绿岩以构造岩片形式出露于阿尼玛卿造山带具缝合带性质的东昆仑南缘断裂附近 ,岩石组合相对简单完整 ,主要由基性熔岩、辉长岩和蛇纹岩 3个单元组成 ,彼此成构造接触关系。来自 3条剖面的的基性熔岩样品主元素、微量和稀土元素地球化学特征显示样品属低钾拉斑玄武岩系列 ,在多种环境判别图解中一致投入 N- MORB区域 ,稀土总量低 ,具有轻稀土亏损型的球粒陨石标准化模式 ,表明该蛇绿岩形成于典型洋脊环境 ,属于西地中海型岩石圈残片 。

Derni Ophiolite is exposed along Dongkunnan suture zone, A'nyemaqen orogens as allochthonous slices. The ophiolite has a simple but complete rock formation: basalts + massive gabbros + metaperidotites. Geochemical study of these basalts surely shows characteristics of typical N MORB. The ophiolite should be grouped into west Mediterranean type and thus, Derni Ophiolite is regarded as relics of Tethys. To be important, it is the northernmost ophiolite of this kind.