摘要
石榴子石是矽卡岩型矿床中最常见的蚀变矿物之一,石榴子石年代学可以准确限定矽卡岩型矿床的成矿时代。长江中下游地区发育众多矽卡岩型铜多金属矿床,东雷湾铜多金属矿床为区内典型的矿床之一,精确的测定其成矿时代对深入了解长江中下游矽卡岩型铜多金属矿床的成因和动力学背景具有重要意义。本文以东雷湾铜多金属矿床含矿矽卡岩中石榴子石为研究对象,运用电子探针(EPMA)和激光剥蚀电感耦合等离子质谱(LA-ICP-MS)等手段分别开展石榴子石微区主量、微量和U-Pb定年工作,以期准确限定矿床成矿时代,并约束成矿流体特征。基于详细的岩相学观察,东雷湾铜多金属矿床中石榴子石具有两种产状,一种为深棕色它形石榴子石Grt1,另一种为浅棕色自形石榴子石Grt2。电子探针成分分析显示,两种石榴子均属于钙铁榴石-钙铝榴石固溶体系列, Grt1和Grt2均富Fe,而Grt2相对富Al。对Grt1和Grt2石榴子石开展LA-ICP-MSU-Pb定年,获得Tera-Wasserburg下交点年龄分别为144.9±1.0Ma(MSWD=0.56,n=29)和142.7±1.8 Ma(MSWD=0.62, n=26),两者在误差范围内一致。基于两类石榴石与黄铁矿、黄铜矿等矿石矿物共生矿物组合关系,推测东雷湾矿床矽卡岩蚀变和铜成矿年龄为144 Ma左右,与长江中下游地区铜陵和部分鄂东南的典型铜多金属矿床成岩、成矿时代基本一致,为晚侏罗世-早白垩世古太平洋板块俯冲背景下岩浆-热液作用产物。
Garnet is one of the most common alteration minerals in skarn deposits,and hence garnet geochronology can accurately constrain the metallogenic epoch of skarn deposits.Many porphyry-skarn type polymetallic deposits are developed in the Middle-Lower Yangtze River Valley metallogenic belt,including the Dongleiwan copper polymetallic deposit.Accurate determination of the mineralization age is significant for understanding the genesis and geodynamic setting of porphyry-skarn type polymetallic deposits in the Middle-Lower Yangtze River Valley metallogenic belt.For this purpose,garnet from the Dongleiwan copper polymetallic deposits was analyzed.To accurately constrain the mineralization age of the deposit and reveal the characteristics of the ore fluids,we conducted electron probe micro analysis(EPMA)major element analysis,inductively coupled plasma mass spectrometry(LA-ICP-MS)trace element analysis,and U-Pb isotopic dating of garnet in ore-bearing skarn,.Based on detailed petrographic observations,garnet of the Donglewan copper polymetallic deposit can be divided into two types.One type is dark brown anhedral garnet(Grt1),and the other type is light brown euhedral garnet(Grt2).EPMA results show that both types belong to andradite to grossularite solid solution series.Both Grt1 and Grt2 are andradite,and Grt2 is relatively richer in grossularite component.LA-ICP-MS U-Pb dating on Grt1 and Grt2 yields Tera-Wasserburg lower intercept 206Pb/238U age of 144.9±1.0 Ma(MSWD=0.56,n=29)and 142.7±1.8 Ma(MSWD=0.62,n=26),respectively,which are consistent within the error range.Considering the intergrowth relationship between the skarn grandite and ore minerals(pyrite and chalcopyrite),the age of skarn alteration and copper mineralization of the Dongleiwan copper polymetallic deposit is constrained to be 144 Ma.Ages of the Dongleiwan deposit are almost identical with other typical magmatic intrusions and deposits in the Jiujiang-Ruichang metallogenic belt,Tongling,and part of Southeast Hubei in the Middle-Lower Yangtze River Valley metallogenic belt.Therefore,they probably formed by magmatic-hydrothermal activity associated with the subduction of the paleo-Pacific plate.
作者
王海
抄尉尉
王颖
钟福军
徐林
吉鸿杰
万卫
文杰
冯道水
王勇
WANG Hai;CHAO Weiwei;WANG Ying;ZHONG Fujun;XU Lin;JI Hongjie;WAN Wei;WEN Jie;FENG Daoshui;WANG Yong(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,Jiangxi,China;Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;The Second Geological Brigade of Jiangxi Provincial Geological Bureau,Jiujiang 332000,Jiangxi,China)
出处
《大地构造与成矿学》
EI
CAS
CSCD
北大核心
2023年第5期1141-1157,共17页
Geotectonica et Metallogenia
基金
放射性地质与勘探技术国防重点学科实验室开放基金项目(2022RGET08)
江西省自然科学基金项目(20232BAB213065)
国家青年科学基金项目(42102101)联合资助。
