锡铁山铅锌矿床的找矿潜力与找矿方向

锡铁山大型铅锌矿床发育有完整的海相喷流沉积系统,包括喷流管道相、近喷口相和沉积相.其中,网脉状蚀变角砾岩带长＞2km、宽＞200m,代表喷流管通相;容矿大理岩长＞3km,宽＞1km,最大厚度＞200m,分布于网脉状蚀变岩的外侧,为喷流沉积岩;穿插于厚层块状大理岩中的非层状铅锌矿体是未喷出海底的含矿热液充填、交代的产物,条带状结构的层状铅锌矿体属喷流沉积相.锡铁山矿床喷流管道系统规模巨大,其大规模的物质供给系统为国内外现已发现的SEDEX铅锌矿床中罕见.现已揭露的锡铁山矿床主体属于喷流沉积系统的中心和近喷口相部分,锡铁山地区还存在巨大规模的层状铅锌矿体(床)尚待发现,同时,在矿床东南方向深部的侧伏延深部位,还具有一定规模的赋存于厚层大理岩中的非层状铅锌矿体.这些大规模层状铅锌矿体的找矿标志层可能不再是大理岩,主要围岩可能是富含炭质、钙质的沉积岩,如深灰-灰黑色的含炭方解石片岩、炭质片岩、方解石绢云片岩等.锡铁山东南部地区的滩涧山群相应赋存层位是大规模层状铅锌矿的主攻找矿方向.

THE EXHALATION-SEDIMENTARY SYSTEM OF XITIESHAN LEAD-ZINC DEPOSIT, QINHAI PROVINCE

Xitieshan lead-zinc deposit is located in north margin of Qaidam basin,Qinghai province,originally contained about 30 million tones of ores with a grade of 8% Zn and10% Pb.The deposit formed in a rift basin at the Ordovician period.An exhalation-sediment system have been recognized in the deposit,which includes pipe,proximal-vent and sedimentary faces.The pipe,altered stockwork zone,is >2km in length and >200m in width and consists dominantly of quartz-albite rock.The marble that contains ore-body occurred in the outside of the pipe is the most important exhalation sedimentary rock,with >3km in length,>1km in width and the biggest thickness >200m.The lead-zinc ore bodies can be divided into two main types like un-bedded and bedded ores.The un-bedded ore bodies occurred discordantly in thick marble contains hydrothermal eruption,and formed subsurface deposition,replacement,and zone refinement by up-flowing hydrothermal fluids in the exhalation period.The bedded ore bodies represent sedimentary face.The deposit that has been disclosed is part of the center or proximal-vent in the SEDEX system.A giant reserve of bedded lead-zinc deposit that represents distal-vent has not been explored,which will been the important exploring object in the next few years.In the main while,some un-bedded ore-bodies are expected occurring in the thick marble in the southeastern deep of the lateral trending direction.The key bed for exploring bedded ores probably is sedimentary rocks which are rich in carbon and Ca instead of marble.The most interesting area prospecting for bedded ores is where Tanjianshan group occurred in the southeastern of the Xitieshan mine.