内蒙古兴安盟杜尔基岩体特征研究

STUDY ON CHARACTERISTICS OF DUERJI INTRUSIVE IN XINGANMENG AREA OF INNER MONGOLIA

内蒙古兴安盟杜尔基岩体位于大兴安岭中南段,岩性主要为中—细粒二长花岗(斑)岩、中—粗粒二长花岗岩、细粒二长花岗岩。岩石化学分析结果属于碱性岩系列,具有高硅、高钾、富碱、过铝、贫铁、镁、钙特征。稀土元素总量平均值为112.43μg/g,球粒陨石标准化曲线整体平缓右倾,具有Eu负异常;微量元素蛛网图解表现为"W"型形态,具有明显的Sr、Ba、Ti负异常,反映了强烈的分离结晶作用存在。4个样品K-Ar全岩法测年结果为100.15～120.29Ma,说明岩体形成于早白垩世。反映杜尔基地区在早白垩世可能处于相对稳定的拉张环境。

Duerji intrusiveis located in the middle part of Da Hinggan Mountains. It includes three kinds of rocks which are fine,media and course grain monzonitic granite.According to bulk compositions, these rocks belong to alkaline igneous protoliths with high Si and K, over-saturated aluminum, characterized by the enrichment of alkaline and low Ca, Fe and Mg contents. Average ∑REE is about 112.43μg/g. Chrondrite-normalized REE patterns of the rocks leap right with negative Eu anomalies.The same patterns of rare elements with negative Sr, Ba,Ti reflect strongly differentiation. These rocks formed in early Cretaceous based on the data which is from 100.15 Ma to 120.29Ma of K-Ar dating of four samoles from the intrusive.these characteristics imply that Duerji intrusive may developed in relative stable rift setting.