Non-chondritic platinum-group element ratios in the Earth's mantle
作者： L. Pattou , J. P. Lorand , M. Gros
DOI: 10.1038/379712A0
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摘要: THE Earth's upper mantle has an overabundance of highly siderophile elements (platinum-group elements, gold and rhenium), relative to what would be expected from equilibrium with the metallic core1–3. This excess is now widely believed have been introduced as a "late veneer" by meteorite bombardment during early Earth history, but after separation core4. Here we report high-precision analyses platinum-group (PGEs) fertile upper-mantle Iherzolites, which show variations in abundances that exceed those chondritic meteorites are thought furnished late veneer5. In particular, Pd/Ir ratio, at about 1.76, significantly greater than known meteorites6. Our results, combined previous indications both non-chondritic nearly PGE ratios few other Iherzolites analysed2,3,7–11, strongly suggest heterogeneous its content on scales ∼100 kilometres. If observed can reconciled plausible meteoritic source, heterogeneity may reflect original spatial variation veneer; otherwise, additional fractionation mechanism seems required.
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