白银厂矿田同位素特征及其流体成矿作用研究

Characteristics of isotopic composition and fluid metallogenesis of the Baiyin Ore Field

白银厂矿田多金属硫化物矿床的石英包裹体水的δD水为-71‰--95‰,δ18O水为-0.09‰-+8.7‰,显示了岩浆水、大气降水、变质水的混合作用.含矿火山岩总硫δ34S∑s(+3.68‰)指示硫主要为深部岩浆来源,并经历了陆壳硫的混染,矿石硫主要来源于围岩.含矿流纹岩中的铅为地幔和地壳的混合铅,矿石铅主要来自围岩的构造活化铅.这些同位素特征研究表明,白银厂矿田经历了两期成矿作用,早期为岩浆流体与大气降水混合成矿;晚期为构造流体与大气降水混合,对流循环成矿.

The δDwater and δ18Owater of water in quartz-inclusions in multimetal-sulphide deposits of Baiyin Ore Field are -71‰--95‰ and -0.09‰-+8.7‰ respectively, indicating a mixture of magmatic water, rain water and metamorphic water. δ34S∑ s(+3.68‰) of country igneous rocks that bear minerals shows that the sulfurs in the Ore Field mainly came from magma in depth, and have also been contaminated by sulfurs from crust, while most of the sulfurs in the ores came from the acid country rocks. Lead in the ore-bearing rhyolites is characterized by a mixture of mantle and crust, but the ores are mainly from tectonically activated wall rocks (rhyolites) due to ductile shearing in the ore deposit. The characteristics of these isotopes indicate two stages of metallogenesis contributed to the metal deposits in the Baiyin Ore Field. The early metallogenesis occured in the process of mixture of magmatic fluid and rain water and the late one in the cycle of mixing fluids of tectonic fluid and rain water.