大兴安岭北段偃尾山铜银矿床流体包裹体与矿床成因类型研究

偃尾山铜银矿床是大兴安岭北段呼中-塔源成矿带内新发现的中小型矿床。矿床围岩蚀变呈面状分布,主要蚀变类型为硅化、碳酸盐化、黄铁矿化、伊利石化、高岭石化和绢云母化。热液成矿期可分为三个阶段:成矿早期石英-黄铁矿阶段(含少量黄铜矿)、主成矿期石英-斑铜矿-黄铜矿-辉铜矿(含铜硫化物)阶段和成矿晚期石英-碳酸盐-萤石阶段(含少量方铅矿和闪锌矿)。该矿床流体包裹体主要为富液相包裹体,也有少量纯气相包裹体,未见含子矿物包裹体。主成矿阶段流体包裹体均一温度为155℃~342℃,峰值集中在160℃~230℃,冰点温度在﹣3.3℃~﹣0.3℃,盐度为0.53%NaC_(leqv)~5.41%Na Cleqv;流体成分以K~+、Na~+、SO_4~(2-)为主,含少量Ca~(2+)和Cl~-,气相成分以H_2O为主,含少量的CO_2;流体δ~(18)O在-11.8‰~-13.72‰之间,δD变化范围在-105‰~-137‰之间。总体上,成矿流体为低温低盐度流体,流体来源主要是大气降水,成矿流体和矿床蚀变-矿化特征显示本矿床可能为高硫型浅成低温热液矿床。流体压力的突然降低可能是成矿物质沉淀的主要机制。偃尾山矿床可能代表了区域上同时代一种新的矿床类型,后续深入研究将有助于认识该区域成矿规律和找矿方向。

Fluid Inclusions and Genetic Type of the Yanweishan Cu-Ag Deposit in the Northern Great Xing'an Range

The Yanweishan Cu-Ag deposit is a newly discovered medium-small deposit in the Huzhong-Tayuan mineralized belt in the northern Great Xing'an Range.The wall rock aheration is widely distributed in this deposit and alteration minerals mainly include quartz,carbonate,pyrite,illite,kaolinite and sericite.Three ore mineralized stages are recognized:early quartz-pyrite stage (containing little chalcopyrite),main quartz-bornite -chalcopyrite-chalcocite stage and late quartz-carbonate-fluorite stage(containing little galena and sphelarite).The fluid inclusions include abundant fluid-rich two-phase inclusions and few pure-gas one-phase inclusions,without daughter mineral-bearing inclusions.The homogenization temperature of main ore-forming stage ranges from 155℃ to 342℃,concentrating in 160℃ to 230℃.The freezing temperature ranges from-3.3℃ to -0.3℃,displaying the salinity of 0.53％ ～5.41％ NaCleqv.The aqueous components mainly contain K +,Na + and SO42-with a little Ca2 + and Cl-,and a mass of H2O and a little CO2 form the gas of fluid inclusions.The δ18 O and δD of ore-forming fluid vary in-11.8‰ ～-13.72‰ and-105‰ ～-137‰,respectively.Overall,the ore-forming fluid belongs to low temperature and low salinity fluids,which emanated from meteoric water.The characteristics of a fluid,alteration and mineralizing suggest that this deposit is of the high sulfidation epithermal type.Rapid decrease of fluid pressure may be the main mechanism of ore-forming materials precipitation.The Yanweishan deposit may represent a new type of deposits in the Huzhong-Tayuan mineralized belt and subsequent research could help understand the metallogeny and clarifying prospecting direction.