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Progressive mixing of meteoritic veneer into the early Earth’s deep mantle

Maier Wolfgang D., Barnes Stephen J., Campbell Ian H., Fiorentini Marco L., Peltonen Petri, Barnes Sarah-Jane et Smithies R. Hugh. (2009). Progressive mixing of meteoritic veneer into the early Earth’s deep mantle. Nature, 460, (7255), p. 620-623.

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URL officielle: http://dx.doi.org/doi:10.1038/nature08205

Résumé

Komatiites are ancient volcanic rocks, mostly over 2.7 billion years old (from the Archaean era), that formed through high degrees of partial melting of the mantle and therefore provide reliable information on bulk mantle compositions1. In particular, the platinum group element (PGE) contents of komatiites provide a unique source of information on core formation, mantle differentiation and possibly core–mantle interaction2, 3, 4, 5, 6, 7, 8. Most of the available PGE data on komatiites are from late Archaean (~2.7–2.9 Gyr old) or early Proterozoic (2.0–2.5 Gyr old) samples. Here we show that most early Archaean (3.5–3.2 Gyr old) komatiites from the Barberton greenstone belt of South Africa and the Pilbara craton of Western Australia are depleted in PGE relative to late Archaean and younger komatiites. Early Archaean komatiites record a signal of PGE depletion in the lower mantle, resulting from core formation. This signal diminishes with time owing to progressive mixing-in to the deep mantle of PGE-enriched cosmic material that the Earth accreted as the ‘late veneer’ during the Early Archaean (4.5–3.8 Gyr ago) meteorite bombardment.

Type de document:Article publié dans une revue avec comité d'évaluation
Volume:460
Numéro:7255
Pages:p. 620-623
Version évaluée par les pairs:Oui
Date:2009
Sujets:Sciences naturelles et génie > Sciences naturelles > Sciences de la terre (géologie, géographie)
Département, module, service et unité de recherche:Départements et modules > Département des sciences appliquées > Unité d'enseignement en sciences de la Terre
Mots-clés:Africa, Archean, Australasia, Australia, Barberton greenstone belt, core, core-mantle boundary, cosmogenic elements, earth, experimental studies, geochemistry, ICP mass spectra, igneous rocks, impacts, komatiite, lower mantle, mantle, mass spectra, metals, outer core, Pilbara Craton, platinum, platinum group, Precambrian, ruthenium, Southern Africa, spectra, volcanic rocks
Déposé le:06 juin 2016 13:49
Dernière modification:09 déc. 2016 14:27
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