安徽贵池铜山岩体SHRIMP锆石U-Pb年代学与岩石地球化学特征研究  

SHRIMP Zircon U-Pb Geochronology,Petrochemical and Geochemical Characteristics of Tongshan Intrusion in Guichi,Anhui Province

作　　者：张智宇[1] 杜杨松[1] 张静[1] 庞振山[2] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室地球科学与资源学院,北京100083 [2]中国地质调查局发展研究中心,北京100037

出　　处：《地质论评》2011年第3期366-378,共13页Geological Review

基　　金：全国危机矿山接替资源找矿项目"长江中下游地区矽卡岩型矿床成矿规律总结及成矿机制研究"(编号20089938);中央高校基本科研业务费专项资金资助(编号2010ZD11)的成果

摘　　要：铜山岩体是长江中下游地区沿江岩浆岩主带中的含矿岩体之一,其形成年龄及岩石成因尚缺乏研究。该岩体主要由石英闪长玢岩、石英二长斑岩和花岗闪长斑岩组成,与铜矿化关系密切。SHRIMP锆石的U-Pb测年结果显示,石英二长斑岩的形成年龄为145·1±1·2Ma,侵位于晚侏罗世的燕山运动中期。岩石的化学成分均显示富硅(SiO2=60·23%～66·23%)、富碱(K2O+Na2O=4·97%～8·72%),低钙(CaO=2·61%～5·66%)、低镁(MgO=1·21%～2·92%)的特征;稀土总量均较低(ΣREE<200μg/g),轻重稀土分异显著[LREE/HREE>12,(La/Yb)N>10],具有弱的正铕异常。岩石地球化学及年代学研究表明:岩石为壳幔混源型,是富集岩石圈地幔经不同程度批式部分熔融形成的玄武质岩浆与下地壳物质同熔后,由混染岩浆上升侵位形成的;产生于板块碰撞后隆起到造山晚期的构造背景。此结果有助于为研究长江中下游沿江地区的区域成岩成矿作用提供重要的地球化学依据。Tongshan intrusion is one of the ore-bearing intrusions in the main magmatic belt along the Middle and Lower Yangtze River area.The precise age of rock-forming and petrogenenis are poorly reported at present.The intrusion mainly consists of quartz diorite porphyry,quartz monzonite porphyry and granodiorite porphyry,and has close relationship with the copper mineralization.The result of SHRIMP zircon U-Pb dating shows that the quartz monzonite porphyry formed in 145.1±1.2 Ma,i.e.,the middle stage of Yanshan movement in the late Jurassic.These rocks are all rich in silicon（SiO2= 60.23% ～ 66.23%） and alkali（K2O ＋ Na2O = 4.97% ～ 8.72%）,and low in calcium（CaO = 2.61% ～ 5.66%） and magnesium（MgO = 1.21% ～ 2.92%）.The total contents of rare earth elements are relatively low（ΣREE 200 μg/g）,the fractionation between LREE and HREE is intensitive [LREE/HREE 12,（La/Yb）N 10],and chondrite-normalized REE patterns show a weak positive Eu abnomality.The studies on geochronology,petrochemistry and geochemistry indicate the magma were crust—mantle mixed sources,i.e.,the basaltic magma sourced from enriched lithospheric mantle by batch partial melting,assimilated the mass of low-crust,then went upwards and emplaced in shallow crust.They occurred under the tectonic setting ranging from post collision uplift to late orogenesis.This can contribute to an important geochemical basis for the study of the regional diagenesis and metallogenesis in the Middle and Lower Yangtze River area.

关 键 词：铜山岩体 SHRIMP锆石U-PB定年 岩石地球化学 长江中下游 

分 类 号：P597.3[天文地球—地球化学]