西华山黑钨矿-石英脉绿柱石中熔融包裹体的成分

The composition of melt inclusions in beryl from wolframite-quartz veins in Xihuashan, Jiangxi Province

借助高温高压技术与电子探针分析,首次获得黑钨矿-石英脉绿柱石中晶质熔融包裹体的主要成分。熔融包裹体的成分主要是SiO2和Al2O3(分别平均为70.72%和13.94%)及少量K2O(2.0%),其他氧化物含量甚低,并且含有大量的挥发分(主要是H2O,达11.56%)。激光拉曼光谱分析表明,熔融包裹体液相中CO2、H2S等含量不高(分别为7.8%和4.3%),气相部分主要是一些还原性气体。熔融包裹体代表HF-H2O-花岗岩体系结晶分异最后阶段残余熔融体的成分,证实脉钨矿床的成矿流体不是单一的热水溶液,而是硅酸盐熔体与超临界流体共存的岩浆-热液过渡性流体,其成矿作用始于岩浆-热液过渡阶段。

With the high-temperature-pressure technique, the crystalline melt inclusions （MI） in beryl from Xihuashan wolframite-quartz veins were homogenized and quenched into glasses. The glasses were analyzed by electron microprobe for the first time. It is shown that they are composed mainly of SIO2（70.72% ） and Al2O3 （ 13.94 % ）, with minor K2O （2.0 % ） and extremely low other oxides. Melt inclusions contain a lot of dissolved volatile components （mainly H2O, up to 11.5 % ）. The liquid-and gas phase of fluids in melt inclusions was analyzed by laser Raman microspectrometry, and the results indicate that CO2 and H2S contents are relatively low in liquid phase （CO2-7.8%, H2S-4.3% ）, whereas gas phase consists mainly of reduced gas. The analyses of glasses represent the composition of residual melt at the final stage of crystallization differentiation in the granite- H2O-HF system. Melt inclusions coexisting with primary fluid inclusions in beryl from wolframite-quartz veins suggest that the ore-forming fluids were not only hydrothermal solution but also magmatic-hydrothermal transitional fluids composed of coexistent silicate melt and supercritical fluid, and mineralization began at the magmatic-hydrothermal stage.