河南省桐柏县破山银矿矿床成因探讨

Discussion on deposit genesis of poshan silver deposit which is in Tongbai county,Henan province

河南省桐柏县破山银矿位处秦岭-大别褶皱系,属围山城金银成矿带西段。矿区出露地层主要为中元古界歪头山组(Pt2w)及零星分布的新生界第四系(Q);矿区位处河前庄倾伏背斜西南翼,构造主要表现为北西向展布的层间滑动断裂带,是区内银矿主要容矿构造;矿体呈不规则似层状、脉状产于层间滑动断裂带中。矿石类型有银矿石、银铅锌矿石和铅锌银矿石三种。本文通过对流体包裹体、同位素地球化学的分析研究认为,矿床可能形成形成于小于5km的浅部环境;成矿流体属于中-温、低盐度、低密度、富CO2的K+-SO2-型流体;成矿(早)中期以变质流体为主,成矿晚期深度变浅,逐渐演化为以大气水为主;成矿时代为燕山晚期。结合对区域成矿背景及控矿条件的分析认为:破山银矿矿床成因类型应属造山型矿床。

Poshan silver mine which is in Tongbai country of Henan province situated in Qinling-Dabie fold zone,belongs to the west section of WeiShancheng silver and gold metallogenic belt.The exposed stratum in mining area mainly is WaiToushan group of Meso-proterozoic（Pt2w） and Some scattered Quaternary of Cenozoic（Q）;Mining area situated in plunging anticline southwest branch of He Qianzhuang,geologic structure mainly is sliding fault zones between layers which extend to the northwest,and this structure is the main ore-containing structure of silver mine in this area;orebody appears in sliding fault zones between layers with irregular quasi laminate or veined shape.Ore has three types that is silver ore,silver-lead-zinc ore and lead-zinc-silver ore.Through the analysis research on fluid inclusions and isotope geochemical,this article considers that the deposit formed in the shallow environment which is less than 5km depth;ore-forming fluid was K^＋-SO^2-type fluid which was intermediate temperate,low salinity,low density,riched in CO2;the metallogenic（early） mid-term mainly was metamorphic fluid,the depth became lower in metallogenic advanced stage and evolved into atmospheric water primarily gradually.Metallogenic epoch was Late-Yanshan period.According to the analysis with regional metallogenic setting and ore-controlling conditions,the author considers that the deposit genetic type of poshan silver deposit should be orogenic type deposit.