北祁连中段毛藏寺花岗闪长岩U-Pb年龄及岩石地球化学特征  

U-Pb Ages and Geochemistry of Maozangsi Granodiorite in North Qilian Mountains,China

作　　者：丁启福 黄增保[2] DING Qifu;HUANG Zengbao(Gansu Mining Development Research Institute,Lanzhou 730000,Gansu,China;Geological Survey of Gansu Province,Lanzhou 730000,Gansu,China)

机构地区：[1]甘肃矿业开发研究院,甘肃兰州730000 [2]甘肃省地质调查院,甘肃兰州730000

出　　处：《西北地质》2019年第4期53-62,共10页Northwestern Geology

基　　金：中国地质调查局“中国矿产地质与成矿规律综合集成和服务（矿产地质志）”项目（DD20160346）

摘　　要：笔者研究了北祁连中段毛藏寺花岗闪长岩体的岩石学、年代学和地球化学特征。毛藏寺岩体主要岩石类型为花岗闪长岩,锆石SHRIMP U-Pb测年获得花岗闪长岩结晶年龄为(456±3)Ma。花岗闪长岩的SiO2含量较高,介于65.1%~73.0%,较低的Mg#值(18~32),K2O/Na2O介于0.82~1.37,A/NKC=0.9~1.1,总体为高钾钙碱性准铝质花岗岩;岩石微量元素组成具富集LILE元素,亏损HFSE元素,轻重稀土分异明显[(La/Yb)N=11.1~34.1],具弱负Eu异常。综合地球化学特征和区域构造演化表明,花岗闪长岩岩浆源区为下地壳变玄武岩石,形成于同碰撞构造背景。This paper reports a detailed study of petrology,U-Pb zircon dating and geochemical characteristic for Maozangsi granodiorite in North Qilian Mountains.The Maozangsi pluton is mainly consisted of granodiorite,and the SHRIMP U-Pb zircon dating yield a magma crystallization age of(456±3)Ma for this pluton.The Maozangsi granodiorite has high SiO2(65.1%~73.0%)and low Mg#(18~32)values,its K2O/Na2O ratio is 0.82~1.37 while its A/NKC ratio is 0.9~1.1,belonging to high K calc-alkaline granite.It is rich in LILE and depleted in HFSE.The REE data shows strongly frantionated REE patterns,with(La/Yb)N ratio of 11.1~34.1 andδEu value of 0.6~0.8.The geochemical characteristics and evolutionary history of granitoids in North Qilian orogen belt indicate that the magma of the granodiorite was derived from partial melting of basaltic rock in lower crust and formed in collisional tectonic setting.

关 键 词：岩石成因 花岗闪长岩 构造意义 北祁连山 

分 类 号：P588.12[天文地球—岩石学] P594.1[天文地球—地质学]