青海化隆地区拉水峡铜镍矿床地质、地球化学特征及成因

    Geology, geochemistry and genesis of the Lashuixia Ni-Cu deposit in Hualong area, Qinghai Province

    • 摘要: 拉水峡铜镍矿床位于化隆基性—超基性岩带中,岩体几乎全岩发生铜、镍硫化物矿化,且已遭受强烈蚀变,以角闪岩为主。岩浆期主要金属硫化物矿物组合为磁黄铁矿、黄铜矿、镍黄铁矿;热液蚀变期主要有紫硫镍矿、黄铁矿、黄铜矿、针镍矿等;氧化表生期主要为含镍高岭石、含镍绿泥石、孔雀石等。矿石轻稀土元素富集和负Eu异常明显,说明岩浆演化过程中发生了大量斜长石等的分离结晶作用。∑PGE含量平均为2460.46×10-9,(Pd+Pt)/(Os+Ir+Ru)值为0.40~2.00,表明铂族元素与岩浆深部熔离作用密切相关;但Pt/Pd(0.01~2.62)、Pd/Ir(0.91~8.77)说明热液作用对铂族元素具有一定的富集作用。S同位素组成变化范围很小,δ34S平均值为2.24‰,硫化物中的S以地幔S为主。拉水峡矿床的形成经历了岩浆融离贯入、热液叠加改造及表生氧化作用3个阶段。

       

      Abstract: The Lashuixia Ni-Cu deposit is located in Hualong basic-ultrabasic belt, Qinghai Province. The Lashuixia rock body was altered intensely, mostly mineralized by Ni-Cu sulfides. The major metal minerals include pyrrhotite, chalcopyrite and pentlandite of the magmatic stage, violarite, pyrite and chalcopyrite of the hydrothermal stage, and nickel-bearing kaolinite, nickel-bearing chlorite and malachite of the oxidation stage. The LREE enrichment and negative Eu anomaly indicate that there probably existed fractional crystallization during the process of magmatic evolution. The average content of ∑PGE is 2460.46×10-9. The(Pd+Pt)/(Os+Ir+Ru) ratios (0.40~2.00) are closely related to the deep magma melting. However, because of the hydrothermal alteration, the ratios of Pt/Pd and Pd/Ir are from 0.01 to 2.62 and from 0.91 to 8.77 respectively. The average value of δ34S is 2.24‰, which indicates that S in sulfides was mainly derived from the mantle. On the whole, the ore-forming processes can be divided into magmatic, hydrothermal and oxidation stages.

       

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