滇西兰坪金顶铅锌矿床精细刻画矿化过程:来自硫化物原位微量元素和S-Pb同位素的证据  

Precise discrimination on the mineralization processes of the Jinding Pb-Zn deposit,Lanping Basin,western Yunnan,China:Evidence from in situ trace elements and S-Pb isotopes of sulfides

作　　者：李相材 王京彬[1,3] 祝新友 李成厚 吴金检 王永彬 石珉 郭宇航 LI XiangCai;WANG JingBin;ZHU XinYou;LI ChengHou;WU JinJian;WANG YongBin;SHI Min;GUO YuHang(Faculty of Land and Resource Engineering,Kunming University of Science and Technology,Kunming 650093,China;Beijing Institute of Geology for Mineral Resources,Beijing 100012,China;Sinotech Minerals Zijin Exploration Co.,Ltd.,Beijing 100012,China;Yunnan Jinding Zinc Industry Co.,Ltd.,Lanping 671400,China;Key Laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Innovation Academy for Earth Science,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Yunnan Key Laboratory of Earth System Science,Yunnan University,Kunming 650500,China)

机构地区：[1]昆明理工大学国土资源工程学院,昆明650093 [2]北京矿产地质研究院有限责任公司,北京100012 [3]中色紫金地质勘查有限责任公司,北京100012 [4]云南金鼎锌业有限公司,兰坪671400 [5]中国科学院地质与地球物理研究所矿产资源研究重点实验室,北京100029 [6]中国科学院地球科学研究院,北京100029 [7]中国科学院大学地球与行星科学学院,北京100049 [8]云南大学云南省地球系统科学重点实验室,昆明650500

出　　处：《岩石学报》2023年第8期2511-2532,共22页Acta Petrologica Sinica

基　　金：中国铜业有限公司重点科技计划项目(048);云南省基础研究重点项目(202201AS070004)联合资助。

摘　　要：金顶铅锌矿床位于中国西南中新生代兰坪盆地,是亚洲第二大铅锌矿床,其巨大的储量和复杂的地质成矿史吸引了众多学者的研究,但在矿床成因和矿化过程的精细描述等方面仍存在较大争议。本文通过详细的野外地质调查并结合硫化物的LA-(MC)ICP-MS微量元素和硫、铅同位素分析对该矿床进行了详细解剖。金顶铅锌矿床的含矿地层为景星组砂岩、云龙组含砾砂岩及灰岩角砾岩。成矿过程可分为2个主要阶段:第Ⅰ阶段早期为浸染状的黄铁矿-白铁矿-闪锌矿-方铅矿,晚期硫化物呈块状且出现天青石;第Ⅱ阶段为闪锌矿-方铅矿-黄铁矿-天青石-重晶石-方解石-石膏阶段。成矿过程中硫化物的原位微量元素和S-Pb同位素表现出规律演化特征。主要金属元素除了以简单的类质同象形式赋存于闪锌矿中,Zn^(2+)与微量元素存在4Zn^(2+)→2Fe^(2+)→Ge^(4+)、2Zn^(2+)→Fe2+→Mn^(2+)、3Zn^(2+)→In^(3+)→Sn^(3+)等复杂的替代关系。综合微量元素和S-Pb同位素演化规律,本文认为金顶铅锌矿的成矿流体早阶段与富含金属的盆地卤水和富含H2S的流体有关,晚阶段则与大气水的混入有关。在后一过程中,大气水萃取了区域上富含Fe、Mn、Tl的红层碎屑岩,进而导致Fe、Mn、Tl等元素含量的升高,同时闪锌矿也表现出更宽范围的微量元素特征和更窄范围的^(208)Pb/^(204)Pb、^(207)Pb/^(204)Pb和δ^(34)S值的特征。由此推断,超大型金顶铅锌矿床是由多来源流体相互叠加而形成,其成矿物质主要来源于兰坪盆地沉积地层。此外,BSR作用在硫酸盐还原过程中起着重要作用,西部矿段还原硫可能还有少量TSR作用的贡献。最后,本文讨论了金顶铅锌矿床的矿床成因和精细矿化过程,综合分析认为它是一个受层间构造控制的、富Cd和Ge等多种分散元素的后生碎屑岩容矿型MVT铅锌矿床。The Jinding Pb-Zn deposit is located in the Meso-Cenozoic Lanping Basin,SW China,which is the second largest Pb-Zn deposits in Asia.It has been studied by many researchers because of its huge reserves and complex geological metallogenic history,however,there are still highly controversial aspects regarding its ore genesis and precise mineralization processes.In this study,we carried out a detailed field geological investigation combined with LA-(MC)ICP-MS trace element and S-Pb isotope microanalysis.The ore-bearing strata of Jinding deposit are sandstones of Jingxing Formation,and sandy-breccias and limestone breccias of Yunlong Formation.The mineralization of the deposit can be divided into two main stages:the stageⅠand stageⅡ.The stageⅠcan be further subdivided into the early stageⅠwhich mainly includes disseminated pyrite,marcasite,sphalerite,and galena;and the late stageⅠmainly including lumpy sulfide and minor celestite;while the stageⅡmainly include sphalerite,galena,pyrite,celestite,barite,calcite,and gypsum.These mineralization stages are characterized by different mineral assemblages and structural characteristics from early to late.Furthermore,the in situ trace elements and S-Pb isotopes of sulfide minerals showed regular evolutionary characteristics during the mineralization.According to the correlation of different trace elements in the sphalerite,the important coupled substitutions are discovered:4Zn^(2+)→2Fe^(2+)→Ge^(4+)、2Zn^(2+)→Fe2+→Mn^(2+)、3Zn^(2+)→In^(3+)→Sn^(3+)and other complex substitution relationships.Based on the evolution of trace elements and isotopes,we conclude that the ore-forming fluids of the Jinding Pb-Zn deposit is related to the basin brine rich in metals and the H 2S-rich fluids in the early stage,and the mixing of meteoric water in the late stage,which extracted the red-bed clastic rocks rich in Fe,Mn and Tl,thus leading to the increase in the content of Fe,Mn,Tl and other elements.In addition,sphalerite also shows a wider range of trace element char

关 键 词：金顶铅锌矿床 LA-(MC)ICP-MS 微量元素 S-Pb同位素 MVT型矿床 

分 类 号：P597.2[天文地球—地球化学] P618.42[天文地球—地质学] P618.53