胶西北焦家金矿深部成矿流体性质及成矿作用

The characteristics of deep ore-forming fluid and metallogenesis of Jiaojia gold deposit, northwest Jiaodong Peninsula

胶东金矿集区因储量和产量巨大,一直是国内外矿床地质学者研究的热点。区内金矿床自西向东集中分布在招(远)-莱(州)断裂带、栖霞断裂带和牟(平)-乳(山)断裂带内。焦家金矿是位于招(远)-莱(州)断裂带内典型的蚀变岩型金矿,矿体赋存于焦家主干断裂的破碎蚀变带内。主成矿阶段石英内流体包裹体岩相学观察表明,焦家金矿主成矿阶段流体包裹体类型为H2O-CO2±CH4包裹体、H2O溶液包裹体和富CO2单相或两相包裹体。空间紧密的不同包裹体内含碳相体积差异较大,但均一温度近似。包裹体均一温度为160~320℃,属高中温热液流体,流体具中低盐度(4%~10%NaCleq)、低密度(0.64~1.10 g/cm3)的特点。流体包裹体激光拉曼测试常见CO2特征的费米共振双峰,少量可见CH4特征峰。通过对比焦家及区内不同金矿成矿流体性质,并结合氢氧、碳及锶钕同位素特征的分析,认为胶东地区蚀变岩型金矿和石英脉型金矿为古太平洋西向俯冲体制下在壳幔边界处发生强烈壳-幔相互作用下的同一构造-岩浆-流体成矿系统的产物,矿区构造应力场方向转变、含矿流体的沸腾及广泛的水-岩蚀变反应是胶东金矿的成矿机理。

Researches of the Jiaodong gold cluster have always been the subjects of discussion among ore geologists, due to the huge reserve and production. Three ore fields distribute along Zhaoyuan-Laizhou fault belt, Qixia fault belt and Muping-Rushan fault belt. Jiaojia gold deposit situated in Zhaoyuan-Laizhou fault belt is typical of alteration rock type gold deposit, ore bodies of which lie in the crashed alteration belts of the Jiaojia main fault. The paper focused on the fluid inclusions of the main mineralizing stage, and came up with that types of fluid inclusions from main mineralizing stage include two or three phases H2O-CO2±CH4 type, two phases aqueous type and single or two phases CO2-rich type. Volum of carbonate phase between spatially tighly related inclusions diverse notability, but are approximate in the homogenization temperature. The homogenization temperatures,salinities and desinies of fluid inclusions from the main mineralization stage rang from 160 ℃ to 320 ℃, 4% to 10%NaCleq and 0.64 to 1.10 g/cm3, belonging to high-mediate temperature, mediate-low soilid, low desinity fluid. Laser laman testing of the fluid inclusions shows feimie resonace sprumme of typical of CO2, and CH4 typical sprumme are occasionally. Contrasting the characteristic of ore fluid, H-O, C and Sr-Nd isotope between Jiaojia and other gold deposit types from Jiaodong Peninsula,it is suggested that altered rock type and quartz vein type gold deposits are both products of the same tectonic-magma-fluid mineralization system insult fron the interaction between crust and mantle,which taken place under the western subduction of Asian Pacific regime during Early Cretaceous. Convertion of structural force field orientation,boiling of ore fluid and wide fluid-rock alteration are the ore forming mechanics of Jiaodong gold deposits.