胶东牟平邓格庄金矿床流体包裹体研究

Fluid inclusions in the Denggezhuang lode gold deposit at Muping,Jiaodong Peninsula

邓格庄金矿是胶东牟平-乳山金成矿带内第二大石英脉型金矿,金主要产于黄铁矿和多金属硫化物石英腑/细脉中。流体包裹体研究表明,邓格庄金矿不同蚀变带岩石和各成矿阶段金矿石中的流体包裹体主要有三种类型:H_2O-CO_2包裹体、CO_2-H_2O±CH_4包裹体和 H_2O 溶液包裹体。早期乳白色石英中主要赋存原生的 H_2O-CO_2包裹体和次生的 CO_2-H_2O±CH_4包裹体;成矿期黄铁矿石英脉和多金属硫化物石英脉中的 CO_2-H_3O±CH_4包裹体主要为原生,随机分布,气液比变化较大,有时出现不同相比例的包裹体共存现象,而 H_2O 溶液包裹体明显沿愈合裂隙分布;在成矿晚期的石英和方解石中主要发育原生 H_2O 溶液包裹体。显微测温结果显示,成矿前(第1阶段)H_2O-CO_2包裹体的完全均一温度(T_(h,TOT),至液相)为254℃至365℃,成矿期(第Ⅱ和Ⅲ阶段)CO_2-H_2O±CH_4包裹体的完全均一温度(T_(h,TOT),至液相)为195～317℃,成矿后(第Ⅳ阶段)H_2O 溶液包裹体的均一温度(T_(h,TOT);至液相)为156～219℃。成矿的初始流体富 CO_2,主成矿期有 CH_4流体加入,成矿晚期则演化为低温的水溶液流体。水/岩反应及流体不混溶可能是邓格庄金矿金沉淀的主要原因。

Degezhuang gold deposit is currently the second largest lode gold deposit in the Muping-Rushan gold belt of Jiaodong Peninsula, eastern China. Gold occurs mainly in pyrite- and polymetallic sulfide-quartz vein/veinlet stockworks. Fluid inclusions in the altered wallrocks and gold ores show C-O-H fluids of three main types, namely H2O-CO2 , CO2-H2O ＋ CH4 and aqueous inclusion. Early milk white quartz contains original H2O-CO2 inclusions and secondary CO2-H2O± CH4 inclusions. In the pyrite quartz vein and polymetallic-sulphide quartz vein, CO2-H2O± CH4 inclusions occur in isolation with large range of HE O/CO2, whereas the aqueous inclusions occur as secondary trails in microfractures cutting earlier quartz grains. On occasion CO2-H2O ± CH4 inclusions with variable aqueous phase were co-occurrence within the same clusters, and mostly homogenize to liquid or vapor at the same temperatures, indicating immiscibility did occur at the deposit. Quartz and calcite in the late ore-forming stage developed original aqueous inclusion. Microthermometric data show the homogenization temperatures （to liquid） of the CO2-H2O inclusions in the early ore-stage fall in the range between 254 and 365℃. Homogenization temperatures, obtained mainly from inclusions with relatively small CO2 ± CH4 bubbles in the main ore-stages, range from 195 to 317℃. Homogenization temperatures （to liquid） of the aqueous inclusions in the late stage range from 156 to 219℃ o The initial auriferous fluids were CO2-dominant, and were gradually evolved into the increased amount of CH4 in the main ore-stages and into HE O-riched fluids with low temperature in the late stage. Fluid-wallrock interaction and fluid immiscibility possibly led to the gold precipitation.