湖南锡田钨锡多金属矿床流体包裹体显微测温和LA-ICP-MS原位分析对成矿流体演化的制约  

Constraints on the Evolution of Ore-Forming Fluids from Microthermometric and In Situ LA-ICP-MS Analyses of Fluid Inclusions in Xitian Tungsten Tin Polymetallic Deposit, Hunan Province

作　　者：周云[1,2] 黄惠兰[1] 于玉帅[1,2] 李芳[1] 谭靖 ZhouYun;Huang Huilan;Yu Yushuai;Li Fang;Tan Jing(Wuhan Center of Geological Survey,China Geological Survey,Wuhan 430205,China;Research Center for Petrogenesis and Mineralization of Granitoid Rocks,China Geological Survey,Wuhan 430205,China)

机构地区：[1]中国地质调查局武汉地质调查中心,湖北武汉430205 [2]中国地质调查局花岗岩成岩成矿地质研究中心,湖北武汉430205

出　　处：《地球科学》2021年第4期1248-1268,共21页Earth Science

基　　金：国家重点研发计划(No.2016YFC0600205);中国地质调查局花岗岩成岩成矿地质研究中心开放基金(No.PMGR202013);中国地质调查局地质调查项目(Nos.DD20190811,DD20160032,DD20190154)。

摘　　要：为了解锡田钨锡多金属矿床的成矿流体演化过程和成矿元素迁移机制,深入揭示成矿机制,指导该地区的下一步找矿勘探工作,对黑钨矿、锡石及透明矿物的流体包裹体进行了岩相学观察、红外显微测温及LA-ICP-MS原位分析.显示锡田钨锡多金属矿床绿柱石、黑钨矿中发育流体-熔体包裹体,均一温度最高可达760℃.早成矿阶段流体均一温度为360~500℃,盐度主要为28.4%~41.5%NaCl_(eqv),主成矿阶段均一温度为280~450℃,盐度主要为3.0%~20.0%NaCl_(eqv).,晚成矿阶段均一温度为120~280℃,盐度为0.4%~6.6%NaCl_(eqv)..LA-ICP-MS分析表明,超临界流体开始出溶时,W、Cu、Mo等元素优先富集于富挥发分气相中,Pb、Zn、Sn、Fe、Mn等元素则更倾向富集于高盐度卤水相中.锡田钨锡多金属矿床成矿流体来源于燕山期浅源花岗岩,钨锡成矿作用始于岩浆-热液过渡阶段,成矿流体具有高温、高盐度和富CO2等特征.成矿流体来自岩浆流体的出溶,演化过程中经历了两次不混溶作用,不混溶相分离过程中,成矿元素选择性迁移,在各相中进行不均匀分配.流体不混溶、水岩反应、流体混合和流体冷却作用是导致该矿床钨锡矿物沉淀的原因.In order to understand the evolution process of ore-forming fluid and the migration mechanism of ore-forming elements in Xitian tungsten tin polymetallic deposit, to further reveal the ore-forming mechanism and guide the next exploration work in this area. The fluid inclusions of wolframite, cassiterite and transparent minerals were studied by petrographic observation, infrared microthermometry and in situ LA-ICP-MS analysis of fluid inclusions. The results show that fluid-melt inclusions are developed in beryl and wolframite in Xitian tungsten tin polymetallic deposit, and the highest homogenization temperature is 760 ℃. At the early stage of mineralization, the fluid homogenization temperature is 360-500 ℃, the salinity is mainly 28.44%-41.50% NaCl_(eqv). At the main mineralization stage, the homogenization temperature is 280-450 ℃, the salinity is mainly 3.0%-20.03% NaCl_(eqv). At the late mineralization stage, the homogenization temperature is 120-280 ℃, and the salinity is 0.35%-6.58% NaCl_(eqv). LA-ICPMS analysis shows that W, Cu, Mo elements are preferentially enriched in the volatile, while Pb, Zn, Sn, Fe, Mn elements are preferentially enriched in the high salinity brine phase. The ore forming fluid in Xitian W-Sn polymetallic deposit comes from Yanshanian granite, and the mineralization of W-Sn started from the stage of magma-hydrothermal transition, and the ore-forming fluid has the characteristics of high temperature, high salinity and rich CO2. The ore-forming fluid comes from the dissolution of magmatic fluid, which has experienced two immiscible processes in the evolution process. In the process of immiscible phase separation, the ore-forming elements migrate selectively and distribute unevenly in each phase. Fluid immiscibility, water rock reaction, fluid mixing and fluid cooling are the main reasons for the precipitation of W-Sn minerals in the deposit.

关 键 词：岩浆-热液过渡 不混溶作用 成矿流体演化 钨锡矿床 锡田 矿床学 

分 类 号：P611[天文地球—矿床学] P575[天文地球—地质学]