北祁连块状硫化物矿床中矿石和主要矿石矿物地球化学特征

CEOCHEMICAL CHARACTERISTICS OF ORES AND MAJOR ORE MINERALS FROM THE MASSIVE SULFIDE EFOSITS IN NORTH QILIAN MOUNTAINS

对北祁连山白银矿田和郭密寺矿田中主要矿床的矿石和矿石矿物组分特征研究表明，由于各矿田的成矿条件和地球化学背景存在差异，造成不同矿床的矿石和矿石矿物元素组合各具特色。但作为同一类型矿床，它们之间又有很多共性，特别是同一矿田内各矿床的地球化学特征具有相似性和过渡性，反映了成矿条件变化的趋势。

Baiyin and Guomisi are important representative massive sulfide orefieldsin North Qilian mountains. A comparative study on chemical composition ofores and major sulfide minerals from the orefields can reveal the following characteristics. In the Baiyin orofield, the Zheyaoshan ore deposit consists chiefly ofcopper ores,and is poor in minor elements ;the Huoyanshan deposit is predo-minated by copper ores associated with some polymetallic ores,with minorelements being mainly bismuth and arsenic;the Xiaotieshan deposit is mainlycomposed of zinc-lead-copper polymetallic ores,associated with gold,silver,mercury,antimony etc. The deposits in the Guomisi orefield are chiefly madeup of zinc-lead-copper polymetallic ores toesorether with some copper-rich andlead-rich ores. Among them,the Xiagou deposit is rich in gold,whereas theGuomisi deposit is rich in bismuth. Although there exists some disparity ofore composition between the two orefields,chemical components of ores fromdifferent deposits show certain connecrion and transitional relationship within the same orefield. Chemical components of sulfide minerals demonstrate that the Baiyin ore- field is characteristlcally rich in cobalt,nickel,tin,barium,mercury,bismuthand mangaliese,while the Guomisi orefield is noted for the richness of arse-nic,antimony,gallium,silver,molybdenum and chromium,This must haveresulted from the difference in metallogenic conditions and geochemical back- ground of the two orefields. The common features of the two orefields are thatfrom the copper(zinc)type ore deposits to the zinc-lead-copper polymetallicdeposits there exists an evolution trend from the high temperature elementassociation to the low temperature elemont association.