西秦岭寨上特大型金矿床成矿作用及成矿模式研究

Study on the Metallogenesis and Mineralization Model of Super-giant Zhaishang Gold Deposit in West Qinling

寨上金矿是微细浸染型金矿床。金的赋存状态有3种类型:一是呈微细粒包体或类质同像替代形式存在于载金矿物中;二是呈微细粒分布在碎屑粒间;三是呈微细粒分布在石英、方解石脉的晶粒间。载金矿物黄铁矿具有特征的增生环带;原生矿石类型主要有浸染状和细—网脉状,极少量的块状矿石。矿床类型有细—中等浸染状破碎带型、细—网脉型。流体包裹体研究表明,成矿流体具有中低温、低盐度、低密度和多期次活动的特点,成矿压力较低,成矿深度较浅。由矿区金的赋存状态、载金矿物的增生环带、矿石类型、矿床类型、流体组成及性质,得知寨上金矿成矿受构造—流体双重作用,由此建立了成矿模式,即浅源和深源成矿物质混合形成成矿流体→成矿流体分异(分层)→先后依次贯入(渗透)→形成脉状(浸染状)矿石(体)。

Zhaishang gold deposit is a micro-fine disseminated gold deposit.Au occurred in three types：micro-fine grained inclusions or isomorphism existed in gold bearing minerals;micro-fine grains distributed among debris particles;as micro-fine grains found in quartz and calcite crystals.Gold-bearing pyrite has characteristics of proliferative zones;primary ore types mainly include disseminated ore and fine-stockwork ore,and very little massive ore.Deposit types are fine-medium disseminated fracture zone type and fine-stockword type.Microthermometry study shows that ore-forming fluid has characteristics of low temperature,low salinity,low densities,multi-period,low pressure and shallower depth.It can be concluded from gold occurrence state,proliferative zones of gold-bearing mineral,ore type,deposit type and ore-forming fluid composition and characteristics,that gold mineralization of Zhais-hang deposit is controlled by dual role of structure and fluid.Thereby establishing a mineralization model for Zhaishang Au deposit：substances of shallow depth and deep depth origins mix to form ore-forming fluid→oreforming fluid differentiation→penetration→form vein type（disseminated） ore.