黔东南罗里金矿包裹体特征及成因探讨

Fluid Inclusion Features and Genesis of the Loli Gold Deposit in Southeastern Guizhou Province

石英脉型金矿是我国南方金矿重要的矿床类型,黔东南黎平罗里金矿就是其中之一。黎平罗里金矿为贫硫化物石英脉型金矿;矿脉相互关系、矿石结构构造和成矿流体盐度等特征均表明其成矿的多期多阶段性;金主要形成于成矿阶段,成矿流体均一温度主要集中在150～300℃,盐度集中在0.36%～15.76%,密度集中在0.59～0.97g/cm3,流体包裹体气相成分主要为H2 O、CO2、CH4和少量的N2;Au的成矿流体在沿构造缝隙上升到地表浅层的过程中与围岩发生交代作用形成蚀变,分出相对富含H2O的流体和相对富含CO2的流体。Phillips通过富CO2流体和贫CO2流体的比较研究,证明CO2在金矿形成过程中的作用是缓冲流体pH值、保持Au在流体中的高含量,并且在有利容矿岩石中使Au沉淀。从某种意义上来说,CO2的含量可以作为石英脉型金矿勘探的标志。

The Luoli gold deposit in Liping County of southeastern Guizhou,just like other gold-bearing quartz deposits in southern China,is a low-sulfide gold-bearing quartz deposit.The characteristics of geology,quartz fluid inclusions homogenization temperature,salinity,and Raman spectrum suggest that the deposit formation process can be divided into 4 stages： vein formation stage,mineral formation stage,carbonate stage and supergene stage.Ore-forming fluid uniformity temperatures concentrate in 150～300℃.The salinity of ore-forming fluid is between 0.36～15.76 6wt%.The mineralization density ranges from 0.59 to 0.97 g/cm3.The fluid inclusion composition is dominated by H2O,CO2,CH4,and N2.When the mineralization fluid of Au rose to the shallow subsurface along fissures,it caused metasomatic alteration with surrounding rocks,separating the fluids rich in H2O and CO2.According to Phillips et al.,CO2 plays the role of pH buffering in gold forming process and keeping the high content of Au in the fluid,making precipitation of Au in the lucrative rocks.In a certain sense,the content of CO2 can be used as an indicator for the exploration of gold deposits of quartz-vein type.