安徽铜陵地区胡村铜矿床流体包裹体研究

摘要

胡村铜矿床位于安徽铜陵狮子山矿田的南部,以矽卡岩型铜多金属矿为主,矿床浅部主要为铜金矿体,深部主要为铜-辉钼矿体.本文对其浅部矽卡岩型铜矿体开展了系统的成矿流体研究.根据矿物学、岩石学、成岩、成矿作用划分为分3个演化阶段:矽卡岩阶段(Ⅰ阶段)(细分为工-1、Ⅰ-2阶段)、石英硫化物阶段(Ⅱ阶段)(细分为Ⅱ-1、Ⅱ-2a和Ⅱ-2b和Ⅱ-2c阶段)和碳酸盐阶段(Ⅲ阶段).流体包裹体主要有富液相(工型)、含子晶(Ⅱ型)、富气相(Ⅲ型)3种类型.不同阶段成矿流体演化特征为:工阶段矽卡岩流体包裹体以高温(543～631℃),中-高盐度(14.8％～20.1％和44％～50.1％ NaCleq,质量分数,下同)为特征;Ⅱ阶段主成矿硫化物阶段流体包裹体以中温(172～298℃),众值范围为210 ～ 230℃,低-中等盐度(5.9％～16.9％)为特征;Ⅲ阶段流体包裹体以中-低温(158～247℃),众值范围为170～190℃,低等盐度(1.7％～6.2％)为特征.H-O同位素研究表明成矿流体源自岩浆水,演化到硫化物成矿阶段为与大气降水混合热液特征.流体包裹体地球化学研究表明胡村矿床浅部矿体成矿作用主要受温度控制,铜在高温状态呈迁移状态,在水-岩反应的影响作用下大气降水与成矿流体不断混合导致流体体系温度快速下降,成矿物质开始沉淀富集成矿.%The Hucun copper deposit,located in the south of the Shizishan deposit in Anhui Province,is a typical skarn-type copper polymetallic deposit,which is mainly characterized by copper-gold orebodies in the shallow and copper-molybdenite orebodies in the depth.A systematic study of its ore-forming fluids of the shallow skarntype copper deposit indicates that three evolutionary stages could be recognized in its rock-forming and ore-forming process,i.e.,skam stage (Stage Ⅰ,subdivided into Ⅰ-1 and Ⅰ-2),quartz sulfide stage (StageⅡ,subdivided into Ⅱ-1,Ⅱ-2a and Ⅱ-2b stages) and carbonate stage (Stage Ⅲ).The results also show that there are three main types of fluid inclusions,namely liquid-rich phase (Type Ⅰ),subcrystal (Type Ⅱ) and gas-rich phase (Type Ⅲ).The evolution of ore-forming fluids at different stages are as follows:it was of high temperature (543～631℃) and moderate-high salinity (14.8％ ～20.1％ and 44％ ～50.1％) at Stage Ⅰ,medium temperature (172～298℃) and low-moderate salinity (5.9 ％ ～ 16.9 ％) at Stage Ⅱ,and medium-low temperature (158～247℃) and low-moderate salinity (1.7％～6.2％) at Stage Ⅲ].H-O isotope studies indicate that ore-forming fluid originated from magmatic water and then was mixed with meteoric water at the sulfide metallogenic stage.Geochemical characteristics of fluid inclusions reveal that the temperature was the main controlling factor for the shallow orebodies,the copper migrated at high temperature and then the ore-forming materials began to precipitate and concentrate to mineralize when the temperature rapidly fell with the continuous mixing of meteoric water and ore-forming fluids.