豫西萑香洼金矿床成矿机制探讨:流体包裹体和稳定同位素证据  

Discussion on metallogenic mechanism of the Huanxiangwa gold deposit in western Henan: fluid inclusion and stable isotope evidence

作　　者：高亚龙 刘馨[1] 简伟 叶会寿 耿艳光[4] 石永兴 金文强 GAO Yalong;LIU Xin;JIAN Wei;YE Huishou;GENG Yanguang;SHI Yongxing;JIN Wenqiang(Key Laboratory of MetaUogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;Tianjin North China Geological Exploration Bureau,Tianjin 300170,China;Institute of Earth Sciences,China University of Geosciences(Beijing),Beijing 100083,China;BGI Engineering Consultants Ltd.,Beijing 100038,China)

机构地区：[1]中国地质科学院矿产资源研究所,自然资源部成矿作用与资源评价重点实验室,北京100037 [2]天津华北地质勘查局,天津300170 [3]中国地质大学(北京)科学研究院,北京100083 [4]北京市勘察设计研究院有限公司,北京100038

出　　处：《地质学报》2022年第3期991-1011,共21页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41972094);中央级公益性科研院所基本科研业务费(编号YYWT-201713)联合资助的成果。

摘　　要：萑香洼金矿位于华北陆块南缘熊耳山地区,是大型的构造蚀变岩-石英脉复合型金矿床。该矿床热液成矿作用经历了4个阶段:黄铁矿-石英阶段(Ⅰ)、石英-黄铁矿阶段(Ⅱ)、石英-多金属硫化物阶段(Ⅲ)和碳酸盐阶段(Ⅳ)。为查明成矿流体的类型、性质、演化特征及成矿物质来源,对脉石英流体包裹体进行了系统的显微测温、成分及H、O、S同位素测试分析,在此基础上,探讨了成矿机制。研究结果表明,第Ⅰ、Ⅱ、Ⅲ阶段主要发育CO_(2)-H_(2)O-NaCl型包裹体和NaCl-H_(2)O型包裹体,以富液相包裹体为主,同时发育少量富气相包裹体,第Ⅳ阶段仅发育NaCl-H_(2)O型包裹体。从早到晚,各成矿阶段包裹体的均一温度分别集中在260-320℃、220-280℃、180-240℃和120-180℃,盐度分别集中在5%-9%NaCleq、7%-12%NaCleq、5%-10%NaCleq和0%-2%NaCleq,成矿流体由早阶段的中温低盐度热液体系向晚阶段的低温低盐度热液体系演化。石英-硫化物(Ⅰ、Ⅱ、Ⅲ)阶段流体气相成分以H_(2)O、CO_(2)为主,含少量的H_(2)S、N_(2)、C_(2)H_(6)、CH_(4)、CO、H_(2)等,液相成分中金属阳离子以Na^(+)为主,阴离子以SO_(4)^(2-)、Cl^(-)为主;碳酸盐阶段成矿流体中多数离子含量较早阶段出现了降低。H-O同位素研究结果表明:第Ⅰ阶段至第Ⅲ阶段的成矿流体δ^(18)O_(水)分别为3.8‰-11.9‰(均值7.7‰)、3.3‰-8.2‰(均值5.2‰)、1.2‰,相应的δD分别为-96‰--72‰(均值-84‰)、-98‰--67‰(均值-87‰)、-90‰,早阶段成矿流体与岩浆热液特征相似,随着成矿作用的进行,大气降水出现一定程度的混入;萑香洼金矿δ^(34)S的值介于-24.2‰-0.6‰,其中成矿早阶段未分馏的δ^(34)S的值主要在0值附近,认为萑香洼金矿硫源与早白垩世岩浆-热液系统或幔源流体相关,二者或参与成矿。萑香洼金矿为早白垩世区域岩石圈减薄、伸展环境下形成的“克拉通破坏型金矿床”。The Huanxiangwa gold deposit is located in the Xiong’ershan gold polymetallic ore district, Henan Province. Two mineralization types are distinguished in the gold deposit: altered cataclastic rocks and quartz vein mineralization. The ore-forming process can be divided into four mineralization stages: pyrite-quartz stage(Ⅰ), quartz-pyrite stage(Ⅱ), quartz-polymetallic sulphides stage(Ⅲ) and carbonate stage(Ⅳ). In order to identify the characteristics and evolution of ore-forming fluids, fluid inclusions in different stages were analyzed by petrography, microthermometry, laser Raman spectroscopy, and gas-liquid chromatography.The sources of ore-forming fluids and ore-forming material were inferred by analyzing the hydrogen, oxygen and sulfur isotopes in typical minerals of each ore-forming stage. Fluid inclusions in the Ⅰ, Ⅱ, Ⅲ stages are mainly NaCl-H_(2)O type and CO_(2)-H_(2)O-NaCl type, which mainly homogenized at temperatures between 260-320℃, 220-280℃, and 180-240℃, respectively, with salinities concentrated in the range of 5%-9%, 7%-12%, and 5%-10%, indicating a moderate temperature and low-salinity ore-forming fluid.In the late carbonate stage, there is only NaCl-H_(2)O type fluid inclusions, which mainly homogenized at temperatures between 120-180℃, with salinity concentrates at 0%-2%. In the quartz-sulfide stage(Ⅰ, Ⅱ, Ⅲ), gas phases in fluid inclusions are mainly composed of H_(2)O, CO_(2), with small amount of H_(2)S, N_(2), C_(2)H_(6), CH_(4), CO and H_(2), and liquid phases are mainly Na^(+), SO_(4)^(2-), and Cl^(-). In the carbonate stage, ion concentrations in the liquid phase decreased significantly. The δ^(18)O_(H_(2)O) values of stage I, stage II, and stage III fluids are 3.8‰-11.9‰(mean value 7.7‰), 3.3‰-8.2‰(mean value 5.2‰), and 1.2‰, respectively, while the corresponding δD_(H_(2)O) values are -96‰--72‰(mean value-84‰),-98‰--67‰(mean value-87‰), and-90‰, respectively. The ore-forming fluid of early stage was dominated by magmatic wate

关 键 词：流体包裹体 同位素地球化学 成矿流体 萑香洼金矿 豫西 

分 类 号：P618.51[天文地球—矿床学]