胶东邢家山矽卡岩型钼矿床成矿流体与成矿机制

Ore-forming fluids and metallogenic mechanism of the Xingjiashan skarn Mo deposit in Jiaodong,China

邢家山矿床是胶东地区发现的大型矽卡岩型钼多金属矿床。通过野外调研,将成矿过程划分为四个阶段:早矽卡岩阶段、晚矽卡岩阶段、石英硫化物阶段和石英-碳酸盐阶段。对不同阶段流体包裹体研究表明,存在液体包裹体(L)、气体包裹体(V)和含子矿物包裹体(S)三类。激光拉曼探针显示流体的气体分类型为H_2O-H_2S,早和晚矽卡岩阶段均一温度集中在375～450℃,盐度存在14%～15%NaCleqv和大于30%NaCleqv两个端元;石英-硫化物阶段均一温度集中在260～340℃,盐度存在8%～12%NaCleqv和大于50%NaCleqv两个端元;石英-碳酸盐阶段流体包裹体均一温度集中在170～200℃,盐度小于10%NaCleqv。该矿床成矿流体具有高温高盐度的特征,且富含H_2S等还原性气体,从矽卡岩阶段到碳酸盐阶段成矿温度和盐度总体有降低的趋势。邢家山钼矿δ^(18) O_(H_2O)值为0.04‰～8.18‰,δ^(13) C_(V-PDB)值为-3. 35‰～-0.73‰,δ^(18) O_(V-SMOW)值为5. 93‰～8. 42‰,δ^(34)S值为6.5～10. 8‰。邢家山矿床成矿流体主要来源于岩浆,后期有大气降水的加入,流体沸腾是成矿的主要机制。

The Xingjiashan Mo deposit is currently a large skarn deposit in the Jiaodong metallogenic province.The hydrothermal activities of mineralization can be divided into four stages:early skarn stage(Ⅰ),late skarn stage(Ⅱ),quartz-sulfide mineral stage(Ⅲ) and quartz-carbonate stage(Ⅳ).The characteristics of the fluid inclusions show that the inclusions can be divided into three types:liquid-rich inclusions(L),vapor-rich inclusions(Ⅴ) and daughter mineral-rich inclusions(S).The results of Roman spectra study show that the volatile phases have H2 S.In the early and late skarn stages,the homogenization temperatures peak value range from 375℃ to 450℃,and the salinities have two ranges 14%~15% NaCleqv and >30% NaCleqv.In quartz-sulfide mineral stage,the homogenization temperatures peak value range from 260℃ to 340℃,and the salinities have two ranges 8%~10% NaCleqv and>50% NaCleqv.In quartz-carbonate mineral stage,the homogenization temperatures peak value range from 170℃ to 200℃,and the salinities ranges 8%~10% NaCleqv and >50% NaCleqv.The values of δ^18 OH2 O,δ^13 CV-PDB,δ^18OV-SMOW and δ^34S are 0.04‰~8.18‰,-3.35‰^-0.73‰,5.93‰~8.42‰ and 6.5‰~10.8‰.These results indicate that the ore-bearing fluid in the early stage is characterized by high temperature and high salinity.The ore-forming fluids are mainly derived from magma.Magma water is major ore-forming fluid,with minor meteoric water in the late stage.Fluid boiling may be the mechanism of large-scale metallogenic precipitation.