锡田印支-燕山期复式花岗质岩浆-热液活动时限和物质来源  

Magma-Hydrothermal Fluid Activity Duration and Material Sources in the Xitian Indosinian-Yanshanian Complex

作　　者：苏红中 郭春丽[2] 伍式崇 侯可军[2] 张彦[4] 

机构地区：[1]中国地质大学,北京100083 [2]国土资源部成矿作用与资源评价重点实验室,中国地质科学院矿产资源研究所,北京100037 [3]湖南省地质矿产勘查开发局四一六队,湖南株洲412007 [4]中国地质科学院地质所,北京100037

出　　处：《地质学报》2015年第10期1853-1872,共20页Acta Geologica Sinica

基　　金：国家重点基础研究发展规划项目(2012CB416704);中国地质调查局地质调查工作项目(1212011220523)资助的成果

摘　　要：锡田钨锡多金属矿田位于湘赣两省交界,南岭成矿带的北部。锡田花岗岩体是一个复式岩体。本文利用LA-MC-ICP MS技术对8个样品的锆石进行了原位微区U-Pb定年和Lu-Hf同位素测试,结果显示其中有4个为印支期(226~225Ma)、另外4个为燕山期(166~158Ma)。印支期花岗岩锆石的εHf(t)值为-4.6^-10.8,两阶段模式年龄TDM2值为2011~1534Ma,根据是否呈正态分布可分为7组;燕山期花岗岩锆石的εHf(t)值为-4.3^-10,TDM2值为1896~1429Ma,可分为5组。相似的Hf同位素组成表明两期花岗岩具有同源性,均源自古元古代晚期至中元古代早期地壳物质的部分熔融。而εHf(t)值变化范围较大且分成很多组可能更主要受控于源区Hf同位素的不均一性。此外,本文利用40 Ar-39 Ar定年方法测得花岗岩顶部石英脉和云英岩中4个白(金)云母的年龄为150~148Ma,这期与成矿有关的热液作用应该与最晚一期岩浆活动有关。通过本次获得的定年数据和对已有的成岩成矿定年数据的总结,本文认为锡田岩体可以分为三个期次,印支期(226~225Ma),燕山期第一阶段(166~158Ma)和燕山期第二阶段(151~141Ma)。The Xitian W-Sn polymetallic ore field is located between the Hunan and Jiangxi provinces,the northern part of the Nanling metallogenic belt.The Xitian granitic pluton is a multi-stage granitic complex.Eight samples were analyzed through LA-MC-ICP MS zircon U-Pb and Lu-Hf isotopes and show that four of them are Indosinian（226~225Ma）,the other four are Yanshanian（166~158Ma）.Thereinto,εHf（t）and TDM2 values of Indosinian granites are-4.6^-10.8and 2011~1534Ma,respectively.According to normal distribution characteristics,εHf（t）values can be divided into seven groups.Similarly,εHf（t）and TDM2 values of Yanshanian granite are-4.3^-10 and 1896~1429Ma respectively.And theirεHf（t）values can be divided into five groups.The similar Hf isotopic compositions indicate the Indosinian and Yanshanian granites are homologous.They were all derived from late Paleo-proterozoic to early Mesoproterozoic partial melting of crust materials.Hf isotope heterogeneity in the source region probably resulted in large-scaleεHf（t）values.Moreover,four muscovite or phlogopite samples from quartz veins and greisens yielded 150~148Ma through the 40 Ar-39 Ar dating methods.This period of the hydrothermal activity and mineralization should be related to the latest magmatic activity.Compared with pre-existing rock-forming and metallogenetic ages,the Xitian granitic body should be divided into three phases,Indosinian（226~225Ma）,the first stage of the Yanshanian（165~158Ma）,and the second stage of the Yanshanian（151~141Ma）.

关 键 词：锡田钨锡多金属矿田 复式花岗岩 LA-MC-ICP MS锆石U-Pb定年 LU-HF同位素 云母Ar/Ar定年 南岭地区 

分 类 号：P618.2[天文地球—矿床学] P588.11[天文地球—地质学]