南秦岭赋存于沉积岩中的金龙山金矿带主要载金矿物黄铁矿、毒砂研究

金龙山金矿是产于南秦岭镇安-旬阳晚古生代沉积盆地细碎屑岩-碳酸盐建造中的微细浸染型金矿.主要载金矿物毒砂、黄铁矿,粒度多为10~100 μm,约为次显微状金颗粒直径的1000倍左右.黄铁矿为含砷黄铁矿,并常作为原生沉积成因草莓状、球菌状黄铁矿的增生环带,因而常规方法无法分离出原生沉积成因黄铁矿与热液阶段黄铁矿、毒砂.用于单矿物化学分析、同位素、热电性测定的黄铁矿样品多为热液改造后多阶段黄铁矿的混合样品,毒砂的含金性比黄铁矿更好.成岩期黄铁矿无砷或砷很低,金矿成矿阶段黄铁矿亏硫,毒砂亏砷.金、砷最大可能是含矿热液带入的,成岩期黄铁矿可能提供了部分硫.黄铁矿的热电系数范围较大,空穴导型、电子导型均有,以空穴型为主.矿带内硫化物的硫同位素呈多垛状产出,但主要集中于6‰~17‰之间.铅同位素反映了造山带特征,与汞锑矿石的铅同位素相近,金锑成矿与深大断裂的活动有关.

CHARACTERISTICS OF PYRITES AND ARSENOPYRITES OFJINLONGSHAN SEDIMENT-HOSTED GOLD DEPOSIT,SOUTHERN QINLING MOUNTAIN

Jinlongshan gold deposit exists in upper Paleozoic fined clastic to carbonate formation of Zhen'an Xunyang, southern Qinling Mountain. Grain size of arsenopyrites and arsenian pyrites,which are main gold carrying minerals,are mostly 10～100 μm.Arsenian pyrites are usually as overgrowth rim of strawberry like or coccus like pyrite that formed during sedimentation and diagenesis. Then it's difficult to separate strawberry like and coccus like pyrites from hydrothermal stage's pyrites and arsenopyrites. Arsenopyrites have the highest gold content. Strawberry like and coccus like pyrites are poor in As and maybe also deficient in Au. Pyrites of mineralization stage are poor in sulfur,while arsenopyrites are poor in arsenic. Gold and arsenic may come from deep with hydrothermal solution. Strawberry like and coccus like pyrites may provide some sulfur. Thermoelectricity coefficient of pyrites varies greatly. Sulfur isotope of sulfides mostly concentrates between 6‰ and 17‰. Lead isotope is characteristically as orogenic zone, close to mercury and antimony mineralization. Metallogenic process of gold and antimony is related to deep and large faults.