胶西北留村金矿成矿流体特征与矿床成因

Ore-forming fluids and genesis of Liucun gold deposit in northwestern Jiaodong Peninsula

留村金矿床位于胶东招远-莱州成矿带南端,是发育于古老变质岩中的小型石英脉型金矿。流体包裹体研究表明,留村金矿成矿流体为中低温、中低盐度的H2O-CO2-NaCl型流体体系,成矿流体从初始H2O-CO2-NaCl体系逐渐演化成简单的低盐度H2O-NaCl体系,主成矿期的温度、压力分别为161~354℃和80~310 MPa。氢、氧同位素研究表明,成矿流体主要源于岩浆热液,后期可能有少量大气水的参与,硫同位素研究表明成矿物质部分来自围岩,同时也有深源硫的加入。减压降温导致的流体沸腾作用可能是留村金矿金沉淀成矿的主导因素。单颗粒黄铁矿Rb-Sr等时线测年数据表明,留村金矿成矿时代为（151.0±2.7）Ma,明显早于胶东地区大规模金成矿事件的时间〔（120±10）Ma〕,说明它们不是一个成矿事件的产物,揭示胶西北在150 Ma左右时可能存在小规模的金矿化事件。

Located in the south of the Zhaoyuan-Laizhou gold ore belt of Jiaodong Peninsula,the Liucun gold deposit is a small typical quartz vein type gold deposit.Petrographic and fluid inclusion studies indicate that gold-bearing fluids of the Liucun gold deposit are characterized by H2O-CO2-NaCl with homogenization temperature being 161～354℃ and pressure conditions being 80～310 MPa at the main gold mineralization stage.Oxygen,hydrogen and sulfur isotope data show that ore fluids were mostly derived from magma.Water-rock interaction led to the formation of more crustal fluids with greater input of crust sulfur.Fluid immiscibility caused by cooling and pressure change was possibly responsible for gold precipitation.The Rb-Sr data of pyrites yield an isochron age of（151.0±2.7） Ma,which is much earlier than the age of most gold deposits in Jiaodong peninsula（（120±10）Ma）.There might have existed a small size gold mineralization in the Jiaodong gold province during 150 Ma.