陕西省华县金堆城斑岩型钼矿床流体包裹体研究

陕西省华县金堆城钼矿床位于东秦岭钼矿带西部,形成于燕山期大陆碰撞体制.矿体产出于金堆城花岗斑岩体内部及其内外接触带.流体成矿过程包括早、中、晚3个阶段,分别以石英-钾长石组合、石英-(钾长石)-多金属硫化物-(碳酸盐)组合和石英-碳酸盐组合为标志,矿石矿物主要沉淀于中阶段.早、中阶段石英中可见纯CO_2包裹体(PC型)、CO_2-H_2O型包裹体(C型)、水溶液包裹体(W型)和含子晶多相包裹体(S型),但晚阶段只发育水溶液包裹体(W型).早阶段C型和W型包裹体均一温度集中于280～370℃,盐度为5.68～11.05 wt%NaCl.eqv;中阶段C型和W型流体包裹体均一温度集中于170～270℃,盐度为5.14～12.63 wt%NaCl.eqv.早、中阶段石英中见S型包裹体,加热过程中子矿物不溶.晚阶段流体包裹体均一温度集中于110～1900C,盐度介于7.17%～11.22 wt%NaCl.eqv之间.估算的早、中阶段流体捕获压力分别为143～243MPa和22～115MPa,推测成矿深度约为2.2～8.1km.金堆城钼矿的成矿流体以富CO_2、贫Cl~-为特征.

Fluid inclusion study of the Jinduicheng porphyry Mo deposit, Hua county, Shaanxi province

The Jinduicheng Mo deposit,Hua County,Shaanxi Province is a giant porphyry Mo deposit formed in the Yanshanian continental collision regime in the west part of the East Qinling molybdenum belt.The ore-body occurs in the Jinduicheng granite porphyry and its inner and outer contact,and the ores are characterized by disseminated multistage stockworks.The hydrothermal oreforming process includes the early,middle and late stages,characterized by mineral assemblages of quartz-potassic feldspar,quartz(potassic feldspar)-polymetal-(carbonate)and quartz-carbonate,respectively.Ore minerals were mainly precipitated in the middle stage.The hydrothermal quartz formed in the early and middle stages contain four types of fluid inclusions(FIs),i.e.pure CO_2 (PC-type),NaCl-H_2O(W-type),CO_2-H_2O(C-type)and daughter mineral-bearing(S-type)fluid inclusions;while the late-stage minerals contain only NaCl-H_2O fluid inclusions(W-type).The homogeneous temperatures of the C-type and W-type FIs in the early stage are mainly 280～370℃,with salinities of ranging from 5.68 to 11.05 wt% NaCl.eqv.The C-type and W-type FIs yield homogeneous temperatures of 170～270℃ and salinities of 5.14～12.63 wt% NaCl.eqv in the middle stage.Daughter minerals in the S-type FIs from the early and middle stage do not melt during heating.FIs of the late stage are homogenized mainly at temperatures of 110 to 190℃,yielding salinities of 7.17 to 11.22 wt% NaCl.eqv.The estimated pressures range from 143～243 MPa in the early stage to 22～115 MPa in the middle stage,respectively,corresponding to depth of 2.2～8.1 km.In a word,the ore-fomring fluids in the Jinduicheng Mo deposit are characterized by high CO2 and low Cl~-.