西天山小于赞金矿成矿流体、成矿年代学特征及其地质意义  

Fluid inclusions and zircon U-Pb age characteristics and their significance for the Xiaoyuzan gold deposit in Western Tianshan

作　　者：于杰 李诺[2,3] 张博 疏孙平[1] 陈衍景 YU Jie;LI NUO;ZHANG Bo;SHU Sunping;CHEN Yanjing(MOE Key Laboratory of Orogenic Belts and Crustal Evolution,Peking University,Beijing 100871,China;Xinjiang Research Center for Mineral Resources,Xinjiang Institute of Ecology and Geography,Chinese Academy of Sciences,Oriimqi 830001,China;Xinjiang Laboratory of Mineral Resources and Digital Geology,Uriimqi 830011,China)

机构地区：[1]北京大学造山带与地壳演化教育部重点实验室,北京100871 [2]中国科学院新疆生态与地理研究所新疆矿产资源研究中心,新疆乌鲁木齐830011 [3]新疆矿产资源与数字地质实验室,新疆乌鲁木齐830011

出　　处：《地学前缘》2018年第5期83-95,共13页Earth Science Frontiers

基　　金：国家重点基础研究发展计划"973"项目(2014CB448000;2014CB440802);国家自然科学基金项目(41572070);中国科学院西部之光项目(2015-XBQN-A-05);新疆维吾尔自治区引进高层次人才专项

摘　　要：小于赞金矿床是产于新疆西天山也列莫顿盆地的浅成低温热液型金矿床,赋存于晚古生代大哈拉军山组火山岩中。矿石类型主要为蚀变岩型和石英脉型,主要发育硅化、黄铁绢英岩化、伊利石化、青磐岩化蚀变。流体成矿过程可分为3个阶段,分别为石英-黄铁矿、石英-玉髓-黄铁矿和石英-方解石-黄铁矿阶段。小于赞金矿床流体包裹体类型单一,主要为水溶液包裹体,可分为纯液相水溶液包裹体(PL类)、富液相水溶液包裹体(L类)和富气相水溶液包裹体(V类)。石英-黄铁矿阶段包裹体均一温度集中于130～190℃,盐度w(NaCleqv.)为0.2%～8.0%;石英-玉髓-黄铁矿阶段均一温度介于115～161℃,盐度w(NaCleqv.)为0.7%～3.4%;石英-方解石-黄铁矿阶段均一温度介于110～138℃,盐度w(NaCleqv.)为0.2%～3.4%。鉴于赋矿角砾凝灰岩的锆石U-Pb年龄为(353.8±1.8)Ma,且被下石炭统阿恰勒河组不整合覆盖,故可将小于赞金矿床的成矿时代限定在(353.8±1.8)Ma至早石炭世维宪期。锆石εHf(t)变化范围为+4.1～+8.4,平均值+6.1,两阶段Hf模式年龄tDM2变化范围为822～1 095 Ma,指示该区岩浆演化过程中有少量地幔物质的加入。综合考量矿床地质特征、流体包裹体特征和成矿时代,认为小于赞矿床为早石炭世低硫型浅成低温热液型金矿。Xiaoyuzan gold deposit is an epithermal deposit in the Yeliemodun basin in Western Tianshan,Xinjiang Province.The ore bodies are hosted by volcanic rocks of the Late Paleozoic Dahalajunshan Formation and mainly consist of altered tuff and quartz veins.The hydrothermal alterations include intense silicification,beresitization,illitization and propylitization.The ore-forming process can be divided into three stages：quartz-pyrite,quartz-chalcedony-pyrite and quartz-carbonate-pyrite.Hydrothermal quartz from the three stages contains only aqueous fluid inclusions of liquid-rich,vapor-rich and pure liquid types,respectively.Fluid inclusions in the three stages were homogenized in temperatures of 130-190,115-161 and110-138 ℃,respectively,with salinities of 0.18-8.0,0.70-3.4 and 0.18-3.4 wt.% NaCl equivalent,respectively.Homogenization temperatures decreased from early to late stages implying the presence of fluid boiling.LA-ICP-MS U-Pb dating of zircons from tuff breccia yielded an Early Carboniferous age（weighted average）of 353.8±1.8 Ma,while the ore bodies were covered by the Aqialehe Formation constraining the age of deposit between 353.8±1.8 Ma and Visean age.The positive zirconεHf（t）values（4.1-8.4）and young two-stage Hf model ages（TDM2,822-1095 Ma）suggest a minor juvenile continental crustal involvement.Based on geological evidence including geological and fluid inclusion characteristics and mineralization age of the deposit,we propose that the Xiaoyuzan gold deposit is an LS type epithermal deposit formed in the Early Carboniferous.

关 键 词：矿床地质 流体包裹体 锆石U-PB年龄 浅成低温热液型矿床 小于赞金矿床 西天山 

分 类 号：P618.51[天文地球—矿床学] P597[天文地球—地质学]