南泥湖-三道庄钼(钨)矿床成矿流体的碳氢氧同位素研究及其启示

Source and evolution of the ore-forming fluid in the Nannihu-Sandaozhuang Mo (W) deposit:Constraints from C-H-O stable isotope data

南泥湖—三道庄钼(钨)矿的成矿阶段从早到晚可以划分为(1)矽卡岩化阶段和角岩化阶段,(2)石英钾长石阶段和退化蚀变作用阶段,(3)石英硫化物阶段以及(4)石英碳酸盐阶段。通过对各阶段流体包裹体的碳、氢和氧稳定同位素研究,认为形成该矿床的成矿流体来源以岩浆源为主,含少量有机质的碳酸盐地层的贡献次之,大气降水可能没有贡献。从矽卡岩阶段到石英硫化物阶段再到石英方解石阶段,成矿流体依次经历了硅酸盐熔体与富挥发分热液流体的不混溶、水岩反应和富气流体的减压沸腾,其中气体的大规模逸出发生在石英方解石阶段。

The hydrothermal ore-forming process of the Nannihu-Sandaozhuang Mo（W） deposit can be divided into four stages,i.e.,from early to late,（1） skarn and hornfels stage,（2） quartz-K-feldspar and retrograde stage,（3） quartz-sulfides stage and（4） quartz-carbonate stage.Based on studies of carbon,hydrogen and oxygen isotopes of different stages,the authors hold that the ore-forming fluid was derived mainly from the magmatic system and subordinately from the carbonate strata with minor organic matter.The atmospheric water probably made very little contribution to the ore-forming process.From early to late stage,the ore-forming process probably experienced immiscibility between melt and volatile-rich hydrothermal fluid,water-rock reaction,and phase separation of CO2 rich gas from ore fluid caused by sudden decompression.