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The Uitkomst intrusion and Nkomati Ni-Cu-Cr-PGE deposit, South Africa : trace element geochemistry, Nd isotopes and high-precision geochronology

Maier Wolfgang D., Prevec S.A., Scoates J.S., Wall C.J., Barnes Sarah-Jane et Gomwe Tafadzwa Sharon. (2017). The Uitkomst intrusion and Nkomati Ni-Cu-Cr-PGE deposit, South Africa : trace element geochemistry, Nd isotopes and high-precision geochronology. Mineralium Deposita, p. 1-22.

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URL officielle: http://dx.doi.org/doi:10.1007/s00126-017-0716-x

Résumé

The Uitkomst intrusion is a tubular mafic-ultramafic layered body that hosts one of South Africa’s largest Ni-Cu-Cr-PGE deposits, Nkomati. The sulphide ore occurs in the form of massive lenses in the immediate quartzitic footwall and as disseminations within peridotite. The chromite ore forms an up to ∼10-m-thick layer in the lower portion of the intrusion. Uitkomst has generally been interpreted as a magma conduit, possibly related to the Bushveld event. Here, we present a new high-precision U-Pb zircon date of 2057.64 ± 0.69 Ma that overlaps with the age of the Merensky Reef of the Bushveld Complex and thus demonstrates a coeval relationship between the intrusions. Based on incompatible trace elements as well as O- and Nd isotope data (εNd −4.5 to −6.2), we show that the Uitkomst parent magmas were contaminated with up to 20% Archean upper crust prior to emplacement, and with up to 15% dolomitic country rock during emplacement. Ore formation at Nkomati was critically aided by substantial devolatisation and removal of dolomitic floor rocks leading to hydrodynamic concentration of sulphide and chromite during slumping of crystal mushes into the trough-like centre of the subsiding intrusion and its footwall.

Type de document:Article publié dans une revue avec comité d'évaluation
Pages:p. 1-22
Version évaluée par les pairs:Oui
Date:2017
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:Afrique du Sud, Ni-Cu-Cr-PGE, Uitkomst intrusion, Nkomati intrusion, dépôts, géochimie
Déposé le:22 nov. 2017 03:06
Dernière modification:22 nov. 2017 03:06
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