黄铁矿标型特征对胶东三山岛金矿深部矿化的启示

Pyrite Typomorphic Characteristics:Implication for Deep Gold Mineralization in the Sanshandao Gold Deposit,Jiaodong Peninsula

黄铁矿成因矿物学研究能够为深部成矿潜力评价提供重要信息。三山岛金矿超深钻孔(ZK96-6,2735.70m)揭露该矿床的矿化现象沿着三山岛断裂仍然可以延伸到深部(-2613^-2684m)。为此,针对三山岛金矿深部钻孔岩芯矿化体(-2613^-2684m)开展了黄铁矿成因矿物学研究,以探讨深部黄铁矿标型特征及其对深部成矿的指示意义。对不同阶段黄铁矿的形态标型进行细致观察,利用电子探针和等离子质谱仪对其进行主量和微量元素分析,利用热电仪对其进行热电性分析。研究结果表明:深部矿化体中石英—黄铁矿阶段脉体中的黄铁矿粒度相比其他阶段的黄铁矿更加粗大,指示成矿流体沉淀黄铁矿时处于强过饱和条件,成矿流体中的还原性硫在形成黄铁矿的过程中大量消耗并导致金硫络合物失稳而沉淀。深部金矿体(-2613^-2684m)黄铁矿微量元素含量在(Au+Bi+Cu+Pb+Zn)-(As+Sb+Ba+Ag+Hg)-(Ti+Cr+Co+Ni)三角投图中的位置指示该处矿体属于矿化中部,暗示深部仍有矿化潜力。黄铁矿热电性分析结果显示,P型黄铁矿出现率(P%)与金品位呈正相关关系,指示金和P型黄铁矿共生,该特征可作为深部金矿找矿的依据,同时也暗示着三山岛金矿的深部仍有巨大的找矿潜力。

The study of genetic mineralogy of pyrite could provide the important information for the estimation of deep mineralization potential. The deep drilling(ZK96-6,2 735.70 m)at the Sanshandao gold deposit uncovered that the mineralization could still extend to the depth(-2 613 m to -2 684 m)along the Sanshandao fault zone.Therefore,this study will focus on the genetic mineralogy of pyrite from the deep drill of Sanshandao gold deposit(-2 613 m to -2 684 m),exploring the indicators of typomorphic characteristics of deep pyrite for the deep mineralization. The detailed observation was given to the geometry typomorphic characteristics of different stages of pyrites. The contents of the major and trace elements of different stages of pyrites were analyzed by electronic probe and ICP-MS,respectively.The thermoelectrometry apparatus was operated in order to explore the thermoelectric characters of all stages of pyrites.The pyrite of quartz-gold-pyrite stage in deep gold orebody shows larger grain size than pyrite in other stages,which indicates that ore-forming fluids in this stage attained the supersaturation condition and amounts of pyrite precipitated.A lot of reduced sulfur could be fixed into pyrite,which led to the destability of Au-S complexes and gold precipitation. Selected trace elements contents of pyrite in deep gold orebody(-2 613 m to -2 684 m)were drawn in the(Au+Bi+Cu+Pb+Zn)-(As+ Sb+Ba+Ag+Hg)-(Ti+Cr+Co+Ni)triangle discrimination diagram,which indicates gold orebody in this location belongs to the middle part of the whole orebody and the depth still has the gold mineralization potential.The occurrence rate of P-type pyrite and the gold grade show positive correlation,which indicates that the coprecipitation of P-type pyrite and gold.This relationship could be used as the criterion for the deep prospecting of gold and also indicate the enormous potential of gold mineralization in the depth of Sanshandao gold deposit.