摘要
Fe-polymetallic skarn deposits are widely distributed in the Qimantag area of western Qinghai Province.Recently,this area has become a major metallogenic belt with most promising ore potential.Geotectonically,it belongs to Eastern Kulun orogenic belt.Mineralization is related to Indosinian (204~237 Ma) diorite,granodiorite and mozonitic granite.Ore-controlling strata are composed of marble and silicalite of middle Proterozoic Langyashan Formation,marble,clasolite,silicalite and andesite-basaltic volcanic rocks of Ordovician-Silurian Tanjianshan Group,and crystalline limestone and clasolite of Carboniferous period.In the ore deposits,three types of skarns are developed,i.e.calcic,magnesian and manganoan types,with the first type being dominant.Calcic skarn is commonly associated with Fe,Cu,Mo,(Pb,Zn) mineralization,magnesian skarn is mainly associated with Fe mineralization,and manganoan skarn is always associated with Pb,Zn (Ag) mineralization.Mineral assemblage of the ores is extremely varied and has certain zonation.Potassic metasomatic phenomena are very entensive in the endo-contact zones of the deposits.In addition to different types of skarns,potassic metasomatism also constitutes one of the important ore-searching indicators.