北大别白垩纪镁铁－超镁铁岩的铂族元素地球化学研究
Platinum-group element geochemistry of Cretaceous mafic-ultramafic rocks in the Northern Dabie
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摘要: 提要：采用镍锍火试金法结合ICP-MS分析了12个北大别白垩纪镁铁－超镁铁岩样品的Ir，Ru，Rh，Pt和Pd的含量，结果显示铂族元素（PGE）的含量较低，原始地幔标准化后的PGE分布模式呈正斜率型， PPGE相对原始地幔略微亏损，而IPGE强烈亏损，Pd/Ir值远高于相应的地幔比值。这些镁铁－超镁铁岩中PGE的强烈分异是地幔低程度的部分熔融过程中，PPGE主要受硫化物控制，而Ir则存在于非硫化物相如尖晶石，可能还有合金之中造成的。同时，铂族元素的分布特征表明这些镁铁－超镁铁岩是岩浆结晶分异的产物。Abstract: Abstract：The contents of platinum group elements (PGE；Ir, Ru, Rh, Pt, Pd) in the Cretaceous mafic-ultramafic rocks of the Northern Dabie have been determined by nickel sulfide fire assay preconcentration, combined with ICP-MS. The PGE abundances for all the twelve samples are low. Primitive mantle-normalized PGE distribution patterns have a positive slope and are slightly depleted in PPGE and strongly depleted in IPGE relative to the primitive mantle with Pd/Ir values far higher than their corresponding mantle ratios. Strong PGE fractionation in the samples is mainly controlled by sulfide phase in the process of low degrees of partial melting of the mantle. Ir occurs in non-sulfide phase such as spinel and possibly also in Os-Ir alloys. The Distribution characteristics of PGE suggest that these mafic-ultramafic rocks are the product of magmatic crystallization differentiation.
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Keywords:
- platinum-group elements /
- Northern Dabie /
- geochemistry /
- mafic-ultramafic rocks
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