大兴安岭中南段查干白旗岩体地质地球化学特征  

Geological and Geochemical characteristics of Chaganbaiqi pluton in the middle-southern part of the Da Hinggan Mountains

作　　者：李伟[1] 管育春 毛启贵[1] 邹滔[1] 徐巧 杨星 LI Wei;GUAN Yuchun;MAO Qigui;ZOU Tao;XU Qiao;YANG Xing(Beijing Institute of Geology for Mineral Resources Co.,Ltd.,Beijing 100012)

机构地区：[1]北京矿产地质研究院有限责任公司,北京100012

出　　处：《矿产勘查》2021年第4期839-848,共10页Mineral Exploration

基　　金：大兴安岭中南段有色金属基地综合地质调查项目(编号:DD20190815)资助。

摘　　要：查干白旗岩体位于大兴安岭中南段西南端。对其进行系统的地质学和地球化学研究有助于丰富对区域花岗岩成因机制及构造背景的认识。岩体主要由黑云花岗斑岩与黑云母花岗岩组成。岩石主量元素显示具高硅(71.04%~77.25%)、富碱(7.87%~8.16%),低铝(12.4%~13.45%)的特征,里特曼指数为1.93~2.21,ACNK值介于1.05~1.16之间,属弱过铝质钙碱性系列。岩石相对富集轻稀土,(La/Yb)N为3.84~12.73,在球粒陨石标准化稀土配分图解中呈右缓倾U型配分模式,具有明显的负铕异常(δEu为0.17~0.44)。微量元素组成显示岩石富集Rb、Th、Pb、Hf等元素,亏损Ba、Sr、P、Ti、Eu等元素,具高分异I型花岗岩特征。在蒙古-鄂霍茨克洋闭合碰撞后的伸展环境下,幔源岩浆底侵作用促使上覆地壳发生部分熔融形成花岗质岩浆,岩浆经过分异演化,最终侵位固结形成了查干白旗岩体。The Chaganbaiqi pluton is located at the southwest end of the central and southern part of the Da Hinggan Mountains.Systematic geological and geochemical studies are helpful to enrich the understanding of regional granite genetic mechanism and tectonic background.The rock mass is mainly composed of biotite granite porphyry and biotite granite.Both are all characterized by high composition of SiO2(71.04%~77.25%)and alkali(7.87%~8.16%),low Al2O3(12.4%~13.45%),and the Rittman index from 1.93 to 2.21,ACNK ratio from 1.05 to 1.16,belongs to weak peraluminous calc-alkaline series.The rocks are relatively rich in light rare earths,and(La/Yb)N from 3.84 to 12.73.In the diagram of chondrite normalized rare earth partition,the distribution pattern shows a right slowly inclined U-shaped distribution pattern,with obvious negative Eu anomaly(δEu from 0.17 to 0.44).Trace element composition shows that the rocks are enriched in Rb,Th,Pb,Hf and depleted in Ba,Sr,P,Ti,Eu and other elements,It has the characteristics of highly differentiated I-type granite.It may be under the extensional environment formed after the closed collision of the Mongolia-Okhotsk Ocean.The underplating of mantle-derived magma promotes the partial melting of the overlying crust to form granitic magma.After differentiation and evolution,the magma finally invaded and consolidated to form Chaganbaiqi intrusion.

关 键 词：花岗岩 地球化学 查干白旗 大兴安岭中南段 

分 类 号：P588.121[天文地球—岩石学]