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豆荚状铬铁矿是蛇绿岩方辉橄榄岩中特征性的地幔单元, 具有低Re高Os含量的特性, 能够抵抗变质、蚀变和风化作用对其 Os 同位素组成的影响. 豆荚状铬铁矿 Os 同位素组成的测量值可以代表其形成时的初始 Os 同位素组成, 为认识大洋岩石圈的形成和演化提供重要证据. 本文报道了河北遵化新太古代蛇绿混杂岩带中 7 个豆荚状铬铁矿全岩的 Re-Os 含量和 Os 同位素组成, Re 含量为 0.019~0.128ng/g, Os 含量为 8.828~354.0 ng/g, 187Os/188Os 比值为 0.11003~0.11145. 3 个 Os 含量>300 ng/g 的块状铬铁矿矿石的 Os/188Os 平均值为 0.11026±0.00005, 在 2.6 Ga 时的 为?0.12±0.06, 表明新太古代对流 187 γ Os上地幔的 Os 同位素组成是球粒陨石型的. 这是迄今为止报道的最古老的蛇绿岩豆荚状铬铁矿的 Os 同位素组成.
The podiform chromite is a characteristic mantle unit in the ophiolitic hodgite characterized by low RE and high Os content, which can resist the influence of metamorphism, alteration and weathering on the Os isotopic compositions of pods The measured values of Os isotopic composition of the ore can represent the initial Os isotopic composition during its formation and provide important evidence for understanding the formation and evolution of the oceanic lithosphere.In this paper, seven pods The Re-Os content and Os isotopic composition of whole chromite rock are 0.019-0.128ng / g for Re content, 8.828-354.0 ng / g for Os content, and 0.11003-0.11145 for Os content. The content of three Os is> 300 The average Os / 188Os of the massive chromite ore with ng / g is 0.11026 ± 0.00005 and 0.12 ± 0.06 at 2.6 Ga, indicating that the Os isotopic composition of the upper mantle of the Neoarchean convection 187 γ Os is a chondrite This is the Os isotopic composition of the oldest ophiolite podiform chromite reported to date.