安徽丁里岩体地质和地球化学特征及LA-ICP-MS锆石U-Pb年龄  

Geological and geochemical characteristics and LA-ICP-MS zircon U-Pb dating age of Dingli granite in Anhui

作　　者：产思维 张家嘉 朱义坤[1] CHAN Siwei;ZHANG Jiajia;ZHU Yikun(Geological Exploration Technology Institute of Anhui Province,Hefei 230031,Anhui,China)

机构地区：[1]安徽省勘查技术院,安徽合肥230031

出　　处：《矿产与地质》2021年第2期249-257,共9页Mineral Resources and Geology

基　　金：安徽省公益性地质工作项目“徐宿弧(安徽段)金多金属矿成矿背景调查”(编号:2016-g-3-34)项目资助。

摘　　要：安徽丁里岩体是徐淮地区出露规模最大的花岗岩体。LA-ICP-MS锆石U-Pb定年获得侵位年龄为(180±2.4)Ma,属于早侏罗世岩浆活动产物。岩体富硅[w(SiO 2)=76.10%~76.65%]、富碱[w(K 2 O+Na 2 O)=8.53%~8.56%]、贫钙[w(CaO)=0.39%~0.45%];稀土配分曲线呈现明显的Eu负异常(δEu=0.21~0.26);微量元素特征显示具有较高的Ga(23.0×10^(-6)~23.5×10^(-6))、Nb(46.7×10^(-6)~48.4×10^(-6))和Y(18.4×10^(-6)~20.7×10^(-6))含量,较低的Sr(10.7×10^(-6)~12.1×10^(-6))、Ba(10.7×10^(-6)~15.5×10^(-6))含量,在微量元素原始地幔标准化蛛网图上显示明显的Ba、Sr和Ti的负异常。以上特征表明:丁里花岗岩为A型花岗岩,可能是地幔玄武岩浆演化或玄武岩浆上升后受地壳不同程度混染或亏损地壳熔融的产物。丁里花岗岩是形成于造山后的伸展环境下的板内花岗岩。Dingli granite is the largest outcropped intrusive body in Xuhuai area,Anhui Province.LA-ICP-MS zircon U-Pb dating age is obtained for(180±2.4)Ma,suggesting that it may be the product of the early Jurassic magmatism.The granite is characterized by high SiO 2 content(SiO 2=76.10%-76.65%),high alkali content(K 2 O+Na 2 O=8.53%-8.56%),but low CaO content(0.39%-0.45%).The REE distribution curve of the granite shows the obvious significant negative Eu anomaly(δEu=0.21-0.26).Trace elements are characterized by high contents of Ga(23.0×10^(-6)-23.5×10^(-6)),Nb(46.7×10^(-6)-48.4×10^(-6))and Y(18.4×10^(-6)-20.7×10^(-6)),but low contents of Sr(10.7×10^(-6)-12.1×10^(-6))and Ba(10.7×10^(-6)-15.5×10^(-6)).There are distinct negative anomalies of Ba,Sr,Ti in the primitive mantle-normalized trace element diagram.It is indicated that Dingli granite is A-type granite,which may be the product of mantle basaltic magma evolution,or basaltic magma being mixed and contaminated by the crust in varying degrees or melting of depleted crust after rising.Dingli granite is an intraplate granite formed in the post-orogenic extensional environment.

关 键 词：A型花岗岩 地球化学 锆石U-PB测年 构造环境 安徽 

分 类 号：P588.12[天文地球—岩石学]