德兴铜矿闪长玢岩SHRIMP锆石U-Pb定年及原位Hf同位素研究  

SHRIMP Zircon U-Pb Dating and Hf Isotope Studies of the Diorite Porphyrite from the Dexing Copper Deposit

作　　者：周清[1,2] 姜耀辉[2] 廖世勇[1] 赵鹏[2] 靳国栋[3] 贾儒雅[2] 刘铮[2] 徐深谋[4] 

机构地区：[1]中国地质调查局成都地质矿产研究所,成都610081 [2]南京大学地球科学与工程学院,南京210093 [3]中国地质调查局南京地质矿产研究所,南京210016 [4]中国石化中原油田分公司勘探开发科学研究院,河南濮阳457001

出　　处：《地质学报》2012年第11期1726-1734,共9页Acta Geologica Sinica

基　　金：国家自然科学基金青年基金(编号41202067;41202048)和重点项目(编号40730313);国家"973"计划(编号2012CB416706;2011CB403105)资助成果

摘　　要：江西德兴铜矿是中国东南部最大的斑岩型铜矿,前人对该矿床的含矿花岗闪长斑岩、成矿物质来源和流体演化等方面已进行了大量研究,却对该矿床内出现的脉状石英闪长玢岩缺乏较多的关注。本研究对德兴斑岩铜矿铜厂矿区的脉状石英闪长玢岩进行了SHRIMP锆石U-Pb同位素定年,获得了一个206Pb/238U谐和年龄加权平均值153.5±2.4Ma(2σ,MSWD=2.5),表明其形成于晚侏罗世(～153.5Ma),可能处于由古太平洋板块向欧亚大陆俯冲引起的弧后或弧内拉张构造环境。对其锆石原位Hf同位素和全岩Nd同位素研究显示该侵入体具有较高的εNd(t)值(～0.5)和εHf(t)值(～4.73),暗示其很可能具有壳-幔混合的物质来源。可见,德兴地区的构造活动既经历了早期(170～171Ma)的由古太平洋板块俯冲形成的陆缘弧环境,又经历了后期(～153.5Ma)的弧后伸展环境,分别形成了与成矿相关的花岗质岩浆和与成矿无关的闪长质侵入体。The Dexing porphyry copper deposit in Jiangxi Province is the largest porphyry copper deposit in southeastern China. Considerable studies have been done on ore hearing granodiorite porphyries, ore forming source and ore forming fluids and etc. However, little concern was given over quartz diorite porphyrites occurring as veins in the copper deposit. This study carried out the SHRIMP U-Pb geochronologic analyses for zircons from the diorite porphyrite veins in the Tongchang mine deposit, yielding a good concordant 206Pb/238U weighted mean age of 153.5±2.4 Ma （2σ, MSWD=2. 5）. The result shows that the magmatism occurred in the late Jurassic, land formed likely in a back-arc or intra-arc extension environment triggered by the subduction of palaeo-Pacific plate. Hf and Nd isotopic analysis produced high εNd（t） （N0.5） andεHf（t） values （～4.73）, indicating that these intrusions have a crust- mantle mixing source. Thus, the Dexing area had not only gone though a continental arc setting in the early period （170～ 171 Ma）, but also gone though an back arc extension setting in the late period （～ 153.5 Ma）, forming the ore-bearing granitic intrusions and ore-barren dioritic intrusions, respectively.

关 键 词：德兴铜矿 闪长玢岩 锆石U-PB定年 HF同位素 

分 类 号：P597.3[天文地球—地球化学]