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    陕西庞家河金矿成矿地质特征及成矿物质来源研究

    Geological characteristics and ore-forming material sources of the Pangjiahe gold deposit in Shaanxi Province

    • 摘要: 提要:庞家河金矿产于既是矿源层又是赋矿主岩的上泥盆统下东沟组绢云千枚岩、变质砂岩中。金矿体主要赋存在膨胀、收缩、分枝、复合及波状弯曲的层间挤压片理化带中。矿体形态简单,主要为似层状、板状及透镜状,矿体沿走向较稳定,但倾向及倾角变化较大。主要金矿物为自然金、银金矿,载金矿物为黄铁矿及毒砂。主要围岩蚀变是中低温黄铁矿化和毒砂化。成矿期主要分为3个不同的阶段,即:石英-粗粒黄铁矿-水云母阶段、细粒黄铁矿-毒砂阶段和黄铁矿-石英-碳酸盐阶段。此外,通过对庞家河金矿硫、氧及铅稳定同位素分析,发现矿石铅主要来源于上地壳,部分来源于地幔。δ34S值揭示了金成矿流体主要来源于地壳流体,部分起源于岩浆。同样,δ18O值显示成矿热液部分来源于岩浆水,大部分来源于变质水。总之,庞家河金矿成矿物质来源是储库混合源。

       

      Abstract: Abstract:Ores in the Pangjiahe gold deposit are mainly distributed in upper Devonian Xiadonggou Formation rocks consisting of chloritized sericite phyllite and blastopsammitic quartz sandstone,which constitute a gold-bearing rock series and abundant source layers of gold. Gold ore bodies are mostly preserved in interlayer compresso-crushed zones which assume expansion, contraction, branching, compounding and wavelike bending. Ore bodies exhibit layered and lenticular shapes. Minerals mainly include native gold and electrum. Gold-bearing minerals are pyrite and arsenopyrite. The relevant gold mineralization alterations include pyritization and arsenopyritization. The metallogenic epoch can be mainly divided into three stages, namely quartz-coarse pyrite-hydromica stage, fine pyrite-arsenopyrite stage and pyrite-quartz-carbonate stage. The analyses of δ34S, δ18O and stable lead isotope show that Pb of gold ore bodies was derived mainly from the upper crust and partly from the mantle. δ34S and δ18O also show that gold ore-forming fluid was derived mostly from the crust and partly from magma in the mantle. In a word, gold ore-forming materials were derived from mixed sources.

       

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