Pb同位素对德兴铜矿成矿物源的制约  

Constraint of Pb Isotope on Ore-forming Source Origin of 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] 刘铮[2] 贾儒雅[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》2013年第8期1124-1135,共12页Acta Geologica Sinica

基　　金：国家自然科学基金青年基金资助项目(编号41202067;41202048);重点项目(编号40730313);国家"973"计划(编号2012CB416706);中国地质调查局项目(编号12120113036000)资助的成果

摘　　要：江西德兴铜矿是中国东部最大的斑岩型铜矿,对于该矿床的成矿物质来源方面还存在较大的争论。为弄清楚德兴斑岩铜矿的成矿物质来源,本文对该矿床铜厂和富家坞矿区中的黄铁矿进行了Pb同位素研究,研究结果显示,铜厂和富家坞矿床中黄铁矿具有较为一致的Pb同位素组成:206Pb/204Pb比值为17.954～18.320(平均值18.097);207Pb/204Pb比值为15.407～15.517(平均值15.476);208Pb/204Pb比值为37.888～38.153(平均值37.999)。该Pb同位素特征以及前人的S同位素特征均表明德兴斑岩铜矿的成矿物质主要来源于地幔,而不是主要来源于赣东北双桥山群新元古代的轻微变质老地层。本研究还通过对国内外近30个斑岩型、矽卡岩型及石英脉型含钼矿床的辉钼矿Re-Os同位素特征进行对比分析,认为德兴铜矿辉钼矿中高的Re和187Os含量也暗示其成矿物质主要来源于地幔。该超大型铜矿可能是在古太平洋板块向欧亚大陆俯冲这一挤压构造环境下,为洋片(P-MORB)中富含Fe3+的岩浆释放出的流体或熔体在上升途中与上覆地幔楔相互作用后的产物。The Dexing porphyry copper deposit,Jiangxi Province,is the largest porphyry copper deposit in eastern China,and there have been some controversies on the ore-forming source of this deposit.This study has carried out the Pb isotope analyses of pyrites from the Tongchang and Fujiawu mine.The results show that the two mines have the consistent Pb isotopes,with 206Pb/204Pb ratios ranging from 17.954 to 18.320 （with a mean of 18.097）,207Pb/204Pb ratios ranging from 15.407 to 15.517 （with a mean of 15.476）,and 208Pb/204Pb ratios ranging from 37.888 to 38.153 （with a mean of 37.999）,respectively.The Pb and previous S isotope features indicate that the ore-forming sources are mainly derived from the upper mantle,other than the Neo-proterozoic meta-sedimentary rocks of Shuangqiaoshan Group.On the basis of comparisons of more than twenty molybdenum-bearing deposits worldwide with porphyry type,skarn type and quartz-vein type,we further attribute the high Re-187Os contents of the molybdenites to a mantle origin.The large scale copper deposit should be emplaced in a continental arc setting coupled with westward subduction of the palaeo-Pacific Plate,and formed by the Fe3＋-rich fluids/magmas released by the P-MORB interacting with the lithospheric mantle wedge.

关 键 词：德兴铜矿 PB同位素 成矿物源 太平洋板块 

分 类 号：P618.41[天文地球—矿床学]