湘西头坡脑汞锌矿成矿流体特征及地质意义  

Ore-forming fluid characteristics and geological significance of Touponao mercury-zinc deposit in western Hunan

作　　者：徐怡然[1] 丁振举[1] XU Yi-ran;DING Zhen-ju(Faculty of Earth Resources,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]中国地质大学资源学院,武汉430074

出　　处：《世界地质》2018年第1期124-139,共16页World Geology

基　　金：环扬子地块构造演化与铅锌多金属成矿地质背景研究基金(12120114016601)

摘　　要：湘西头坡脑汞锌矿床位于扬子陆块东南缘,矿床受北西向构造带控制,赋矿围岩为寒武系中统敖溪组第三段细晶白云岩,矿石矿物主要为辰砂及闪锌矿,脉石矿物主要为石英、白云石及方解石。头坡脑汞锌矿床矿石中的流体包裹体主要为纯液相包裹体,部分气液两相包裹体及少量纯气相包裹体。成矿流体具有中低温(84.3℃~183.9℃)、中高盐度(6.16 wt%~22.24 wt% NaCl)及中高密度(0.97~1.10 g/cm^3)等特征。气相成分测定显示包裹体中气相成分主要为CH_4,少量N_2及CO_2,液相成分为H_2O,成矿流体富烃。氢氧同位素组成分别为δD(-105×10^(-3)^-46×10^(-3))和δ^(18)O_(H_2O)(-7.1×10^(-3)~11.4×10^(-3)),指示成矿流体主要为建造水,也有大气降水的加入。根据头坡脑汞锌矿床成矿地质背景、流体特征、流体来源及区域成矿特点,认为本区汞成矿事件应当为上扬子台褶带构造运动长期性和持续性的产物。Touponao mercury-zinc deposit lies in the southeastern margin of Yangtze block,which is controlled by NW trending fault.The ore-hosting rocks are aplite-dolomites from the third member of Middle Cambrian Aoxi Formation.Ore minerals mainly consist of sphalerites and cinnabars,while the gangue minerals comprise quartz,dolomite and calcite.The fluid inclusions in ores are mainly pure liquid inclusions,partially gas-liquid two-phase inclusions and a few pure gas inclusions.The ore-forming fluid is characterized by medium-low temperature(84.3℃~183.9℃),middle-high salinity(6.16 wt%~22.24 wt%NaCl)and medium-high density(0.97~1.10 g/cm 3).The gas composition analysis shows that it consists of CH 4,a small amount of N 2 and CO 2,the liquid component is H 2O,and the ore-forming fluid is hydrocarbon-enriched.The hydrogen and oxygen isotopic compositions areδD(-105×10-3^-46×10-3)andδ18 O H 2O(-7.1×10-3~11.4×10-3),indicating that the ore-forming fluid is mainly formation water,with some meteoric water.According to the geological background of mineralization,fluid characteristics,fluid sources and regional metallogenic characteristics,the authors suggest that mercury mineralization event is resulted from the long-term and durative tectonic movement in the Yangtze fold belt.

关 键 词：湘西地区 汞锌矿 流体包裹体 成矿流体 氢氧同位素 

分 类 号：P618.43[天文地球—矿床学] P618.68[天文地球—地质学]