西藏阿翁错地区多仁组火山岩地球化学特征及其意义

Dorin Formation Volcanic Rock Geochemical Features and Significance in Awon Co Area,Tibet

阿翁错地区多仁组火山岩是班怒带火山岩重要组成部分之一。其呈夹层状分布于多仁组中段,属于钠质低镁亚铝质钙碱性系列安山岩。具有中等Si O2含量、高Al2O3含量、低Ti O2含量、富集轻稀土元素(LREE)、亏损重稀土元素(HREE)、未见明显的负Eu异常显示、富集大离子亲石元素、亏损高场强元素等地球化学特征。研究表明,在区内形成多仁组安山岩的构造环境是与洋壳俯冲有关的岛弧环境,而间断性岛弧型火山岩浆活动则是多层状安山岩形成的直接成因。

The Dorin Formation volcanic rock is one of major components of the Banggong Co-Nujiang volcanic rock belt.The volcanic rocks present interbeds in middle part of Dorin Formation belong to sodic low magnesium sub-aluminous calc-alkaline series andesite.The rocks have geochemical features of medium Si O2,high Al2 O3 and low Ti O2 contents,LREE enriched and HREE deficient,without obvious negative Eu anomaly indications,large ion lithophile elements enriched and high field intensity elements deficient etc.The study has shown that the structural environment to form Dorin Formation andesite is an island arc environment related to ocean crust subduction,while the discontinuity island type volcanic magmatic activities are the direct genesis of multi-layered andesite.