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Gold-bearing quartz veins of the Taihua Group consisting of Archean metavolcanic rocks are a main gold deposit type in the Xiao Qinling area,one of the three biggest gold production areas in China.The quartz veins experienced strong alteration characterized by a typical mesothermal hydrothermal altered mineral assemblage.The grade of gold is affected by the contents of sulphides,e.g.galena,pyrite and chalcopyrite.Results of minor elements analysis for the of gold-bearing quartz veins indicate higher contents of Au and high contents of Ag,Pb,Cu,Cd,W,and Mo.Abundant fluid inclusions were found in the gold-bearing quartz veins.Three types of fluid inclusions were identified:(1) aqueous inclusions;(2) CO 2-bearing inclusions;and(3) daughter crystal-bearing fluid inclusions.Homogenization temperatures ranged from 110 to 670℃ with low and high peaks appearing at 160 180℃ and 280 300℃,respectively.The salinity of aqueous inclusions varies between 1.8 wt% and 38.2 wt% NaCl.The homogenization temperature and salinity show a positive correlation.The H and O isotopes of fluid inclusions in the gold-bearing quartz veins indicate that magmatic solution and metamorphic hydrothermal solution,together with meteoric water,were involved in the formation of gold-bearing fluid.Mesozoic magma activities related to granite intrusions should be the main source of CO 2 fluid with higher temperature and salinity.
Gold-bearing quartz veins of the Taihua Group consisting of Archean metavolcanic rocks are a major gold deposit type in the Xiao Qinling area, one of the three biggest gold production areas in China. Quartz veins experienced strong alteration characterized by a typical mesothermal hydrothermal mineral assemblage. The grade of gold is affected by the contents of sulphides, eggalena, pyrite and chalcopyrite. Results of minor element analysis for the of-gold-bearing quartz veins of higher contents of Au and high contents of Ag, Pb, Cu, Cd, W, and Mo. Abundant fluid inclusions were found in the gold-bearing quartz veins.Three types of fluid inclusions were identified: (1) aqueous inclusions; (2) CO 2-bearing inclusions; and (3) daughter crystal- bearing fluid inclusions. Homogenization temperatures ranging from 110 to 670 ° C with low and high peaks appearing at 160 ° C and 280 ° C, respectively. The salinity of aqueous inclusions varies between 1.8 wt% and 38.2 wt% NaCl. The homogeniza tion temperature and salinity show a positive correlation. The H and O isotopes of fluid inclusions in the gold-bearing quartz veins indicate that magmatic solution and metamorphic hydrothermal solution, together with meteoric water, were involved in the formation of gold-bearing fluid. Mesozoic magma activities related to granite intrusions should be the main source of CO 2 fluid with higher temperature and salinity.