四川平武县金洞沟金矿地质特征及其成因探讨

Geological Characteristics and Genesis of the Jingdonggou Gold Deposit in Pingwu County,Sichuan Province

金洞沟金矿床是位于四川省北部平武县境内的小型岩金矿床。在详细研究矿床地质特征的基础上,测试了石英包裹体均一温度、盐度、化学成分及H、O同位素组成,分析了金属硫化物（黄铁矿、方铅矿、闪锌矿）的S同位素组成,对金的成矿作用进行了深入探讨。研究结果表明：金洞沟金矿床为低温热液型金矿床,其成矿物源主要是志留系茂县群浅变质碎屑岩系,矿石中硫化物以黄铁矿为主,硫化物含量约1%,为少硫化物型矿石。流体包裹体及S、H、O同位素研究显示成矿流体是主要由大气降水组成的热液,成矿温度为125～185℃,平均温度为148.7℃,属低温热液型金矿床。在此基础上,提出金洞沟金矿床的成矿作用经历了原始含矿岩系（矿源层）的形成、区域变质作用衍生矿源层的形成、热液成矿作用及表生氧化富集等4个阶段,韧性剪切构造活动是引起金活化、迁移和富集的主要因素。该成果为该矿床成因的认识和找矿工作提供了参考。

Jindonggou gold deposit is a small gold deposit located in Pingwu County,north of Sichuan Province.Based on a studied geological characteristics of the Jindonggou gold deposit,the authors measured the homogenization temperature,salinity,chemical composition,as well as H and O isotopic compositions of the fluid inclusions of the quartz,measured S isotopic composition of the metal sulfide（pyrite,galena and sphalerite）,and systematically discussed the metallogenesis of the gold deposit.The results show that the deposit belongs to epithermal gold deposit type.The ore-forming source comes from the epimetamorphic clastic rocks of Smx（Silurian System）.This gold deposit is characterized by a poor content of sulfide minerals（below 1%）.Metallogenic fluid is composed of atmospheric precipitation.The homogenization temperature of fluid inclusions ranges from 125 ℃ to 185 ℃,belonging to epithermal gold deposit type.The metallogenesis of the Jindonggou gold deposit is divided in to four stages,i.e.the formation of gold source bed in the sedimentation,the formation of derivative gold source bed in the regional metamorphism,the formation of the gold deposit in the hydrothermalism and hypergenesis.The regional shear zone movement is likely the major factor leading to activation,migration and concentration of Au.The conclusions are significant for realization of the deposit genesis and mineral exploration.