海南岛石门山钼多金属矿床年代学、源区特征及其岩浆氧逸度对成矿作用的启示  

Age and Source of the Shimenshan Molybdenum Polymetallic Deposit in Hainan Island and its Implications on Influence of Magmatic Oxygen Fugacity

作　　者：朱昱桦 许德如[2,3] 张嘉玮 何妙玲[1] 陈根文 单强[2] 王智琳[4] ZHU Yuhua;XU Deru;ZHANG Jiawei;HE Miaoling;CHEN Genwen;SHAN Qiang;WANG Zhilin(Guizhou Geological Survey,Bureau of Geology and Mineral Exploration and Development of Guizhou Province,Guiyang 550081,Guizhou,China;CAS Key Laboratory of Mineral and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,Jiangxi,China;MOE Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,School of Geosciences and Info-Physics,Central South University,Changsha 410083,Hunan,China)

机构地区：[1]贵州省地质矿产勘查开发局,贵州省地质调查院,贵州贵阳550081 [2]中国科学院,广州地球化学研究所矿物学与成矿学重点实验室,广东广州510640 [3]东华理工大学,核资源与环境国家重点实验室,江西南昌330013 [4]中南大学地球科学与信息物理学院,有色金属成矿预测与地质环境监测教育部重点实验室,湖南长沙410083

出　　处：《大地构造与成矿学》2023年第2期376-395,共20页Geotectonica et Metallogenia

基　　金：国家自然科学基金重点项目(41930428);国家重点研发计划深地资源勘查开采重点专项(2016YFC0600401、2017YFC0602302)联合资助。

摘　　要：石门山钼(铅‒锌‒银)多金属矿床为中等规模(金属Mo=1万吨)、高品位(Mo=0.17%)的斑岩型矿床,位于海南岛西南部近东西向九所‒陵水断裂带北西侧的千家复式岩体内,赋矿岩石主要为黑云二长花岗岩和云英岩,矿石类型主要为石英脉型和云英岩型。为了精确厘定该矿床的年代学格架,进一步了解岩石源区特征和成岩成矿的物理化学条件,对采自矿区内的黑云二长花岗岩进行了LA-ICP-MS锆石U-Pb定年,获得^(206)Pb/^(238)U加权平均年龄为94.5±1.6 Ma(MSWD=3.7,n=16),同时分别获得1件石英脉型和云英岩型辉钼矿Re-Os同位素模式年龄为77.9±0.6 Ma、89.6±2.4 Ma。结合已报道的年代学数据,发现该矿床具有明显的两个钼成矿期,分别为89~90 Ma和78~80 Ma,均为晚白垩世早期的产物,且成岩与早期成矿时差接近,具有同源的可能性;黑云二长花岗岩锆石ε_(Hf)(t)值为−10.20~−2.52,二阶段地壳模式年龄t_(DM2)峰值为1.4~1.5 Ga,表明其主要来源于中元古代下地壳的重熔,该时期可能是海南岛钼矿床赋矿花岗质围岩源区的主要形成时期。两种方法计算的全岩锆饱和温度分别为729~785℃(平均753℃)、679~744℃(平均700℃),锆石Ti温度为604~760℃(平均676℃),反映其源区很可能经历了富水条件下的熔融过程。锆石氧逸度计算结果表明其源区处于较强的氧化环境,有利于该矿床的形成。The medium-scale Shimenshan Mo(Pb-Zn-Ag)polymetallic porphyry deposit(10000 t Mo@0.17%)is located in the southwestern Hainan Island.It occurs within the Qianjia pluton northwest of the near E-W trending Jiusuo-Lingshui fault zone.The ore bodies are hosted mainly in the biotite monzonitic granite and greisen,consisting of quartz vein and greisen ore types.In order to accurately determine the formation age of the deposit,zircon LA-ICP-MS and molybdenite Re-Os dating were carried out.LA-ICP-MS analyses on zircon from the biotite monzonitic granite yielded a weighted average age of 94.5±1.6 Ma(MSWD=3.7,n=16),and the molybdenite Re-Os isotope model ages are 89.6±2.4 Ma for greisen type and 77.9±0.6 Ma for quartz vein type,respectively.In combination with the reported geochronological data,it was concluded that there are two stages of Mo mineralization,i.e.,89 Ma to 90 Ma and 78 Ma to 80 Ma in the Shimenshan Mo deposit,and the former is consistent with that of the biotite monzonitic granite within the error.The zircon ε_(Hf)(t) values of the biotite monzonitic granite vary from−10.20 to−2.52 and the peak of two-stage crustal model age t_(DM2) is 1.4 Ga to 1.5 Ga,indicating a derivation from remelting of the middle Proterozoic lower crust.The Zr saturation temperatures estimated by two methods are 729℃to 785℃(average 753℃)and 679℃to 744℃(average 700℃),respectively,and the Ti in zircon geothermometer is 604℃to 760℃(average 676℃),indicating that the melting tool place under water-rich conditions.The zircon oxygen fugacity index calculation further revealed a strong oxidizing environment,which is beneficial for the formation of the deposit.

关 键 词：锆石U-Pb定年 锆石HF同位素 锆石温度计 氧逸度 辉钼矿RE-OS定年 钼矿床 海南岛 

分 类 号：P597[天文地球—地球化学] P611[天文地球—地质学]