陕西穆家庄铜矿床后生成矿作用的流体地球化学证据

Evidences of the epigenetic mineralization processand geochemical features of Mujiazhuang copper deposit

尽管秦岭泥盆系铅锌金多金属成矿带成矿作用均与热水喷流沉积作用有关,柞山地区却有别于凤太地区,具有独特的铜矿成矿背景。流体包裹体研究揭示了后生成矿流体的两阶段流体演化过程:第一阶段的成矿流体为中温,中高盐度岩浆热液含CO2的NaCl-H2O流体。均一温度为190～265oC,盐度12.5～35.34(wt%NaCl),压力12.8～21.3MPa,在同一寄主矿物中均一温度变化小,而盐度变化极大,是岩浆流体沸腾的产物;第二阶段成矿流体为中高温,中高盐度岩浆期后热液NaCl-H2O流体。均一温度为300～350oC,盐度7.4～41.59(wt%NaCl),压力10.8～19.3MPa。反映了岩浆期后热液流体的二次沸腾。应用流体地球化学的综合方法(包裹体流体组成、演化)识别出后生交代流体性质。穆家庄铜矿的成矿流体第一阶段为岩浆水,第二阶段的成矿流体为岩浆水加部分地层水(建造水)。氢氧同位素分析也支持上述结论。

Although Qinling lead-zinc ores belt related to hydrothermal sedimentary, Zhashan area has more special copper metallogenic background than that of Fengtai area— geological setting, basal of basis. On the basis of fluid inclusions of the Mujiazhuang copper deposit, it is showed that there were two stages of fluid evolution. The first stage is magma hydrothermal with middle temperature, middle and high salinity(CO 2)-H 2O-NaCl fluid, which homogenization temperature are 190~265oC and salinity 12.5~35.34(w t%NaCl),pressure 12.8~21.3MPa.Meanwhile, a large of three facies fluid inclusions with a salty crystal coexistence to vapour faices inclusions are discovered in the high and middle high temperature steps of homotemperature of fluid inclusions for the Mujiazhuang copper deposit. It is suggested that the mineralization fluid is over-saturation and occurring boilization and supposed that there is magma chamber in deep of mining area. The second stage is behind hydrothermal of magma with middle-high temperature, middle and high salinityH 2O-NaCl fluid, which homogenization temperature are 300~350oC and salty 7.4~41.59(w t%NaCl),pressure 10.8~19.3MPa.Boilization is an important mechanism of mineral matters precipitation.On the basis of Geochemistry of fluid inclusion(fluid composition, fluid evolution), it is approved that the mineralization fluid is from the magma water in the Mujiazhuang(the first stage), and is from the formational water and the deep-derived magma in the Mujiazhuang (the second stage). In addition, the hydrogen and oxygen isotopic data of the Mujiazhuang copper deposit supports the results.