内蒙古扎兰屯地区印支期二长花岗岩构造演化:来自地球化学特征和锆石U-Pb年龄的制约  

Tectonic evolution of Indosinian monzogranite in Zhalantun area,Inner Mongolia:Constraints of geochemistry and zircon U-Pb age

作　　者：刘文斌 杨延伟 刘翔 班宜红[2] LIU Wenbin;YANG Yanwei;LIU Xiang;BAN Yihong(The first Institute of Resources and Environment Survey of Henan Province,Zhengzhou 450000,Henan,China;Geological Exploration Institute,Henan Bureau of Geology and Minaral Resources Exploration,Zhengzhou 451464,Henan,China)

机构地区：[1]河南省资源环境调查一院,河南郑州450000 [2]河南省地质矿产勘查开发局第二地质勘查院,河南郑州451464

出　　处：《地质通报》2021年第5期698-706,共9页Geological Bulletin of China

基　　金：内蒙古自治区地质勘查基金项目《内蒙古自治区呼伦贝尔市沃力嘎沟等四幅1∶5万区域矿产地质调查》(编号:NMKD2014-22)

摘　　要：扎兰屯地区位于贺根山-黑河构造带中段,区内发育韧性变形叠加的印支期花岗岩。对扎兰屯西北地区印支期糜棱岩化二长花岗岩进行了详细的岩石学、岩石地球化学和锆石U-Pb同位素测年,探讨其岩石成因及区域动力学背景。通过LA-ICP-MS锆石测年获得扎兰屯西北地区糜棱岩化二长花岗岩的结晶年龄为242.1±1.8 Ma,形成时代为中三叠世。地球化学研究显示高硅、高碱、低钙镁特征,属于准铝质-弱过铝质高钾钙碱性花岗岩。岩体富集大离子亲石元素(Rb、U、Th、K),亏损高场强元素(Nb、Ta、Ti),具Zr、Hf正异常,总体表现为不相容元素逐渐富集,Sr、P、Ti亏损程度增加,表现出中等强度负Eu异常。结合区域资料认为,印支期二长花岗岩形成于古亚洲洋闭合碰撞造山后,构造环境由挤压向板内稳定-伸展的变迁阶段。The Zhalantun area is located in the center of the Hegenshan-Heihe structural belt.Indosinian granites with superimposed ductile deformation are developed in the area.Based on the detailed studies on petrology,lithochemistry and zircon dating of the Indosinian mylonitized monzonitic granite in the northwestern Zhalantun area,its petrogenesis and regional dynamics background are discussed.LA-ICP-MS zircon dating yields the crystallization age of 242.1±1.8 Ma for the mylonitized monzonitic granite,indicating it was formed in the Middle Triassic.Geochemical studies show that it is of quasi-aluminum-weak peraluminous high-potassium calcium-alkaline granites with high silicon,high alkali,low calcium and magnesium.It is enriched in large ion lithophile elements(Rb,U,Th,K),depleted in high field strength elements(Nb,Ta,Ti),with positive Zr and Hf anomalies,and in general,incompatible elements are gradually enriched.The increasingly depletion of Sr,P and Ti and the moderate negative Eu anomaly were observed.Based on the regional data,it is suggested that the Indosinian monzonitic granite was formed in the compression-extension transition stage of the tectonic environment after the Paleo-Asian Ocean closed collision orogeny.

关 键 词：二长花岗岩 锆石U-PB定年 印支期 扎兰屯地区 内蒙古 

分 类 号：P534.51[天文地球—古生物学与地层学] P588.121[天文地球—地质学]