Fluid inclusion study of the Jinduicheng porphyry Mo deposit, Hua county, Shaanxi province
陕西省华县金堆城斑岩型钼矿床流体包裹体研究

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~-.