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The Kabanga Ni sulfide deposits, Tanzania: II. Chalcophile and siderophile element geochemistry

Maier Wolfgang D. et Barnes Sarah-Jane. (2010). The Kabanga Ni sulfide deposits, Tanzania: II. Chalcophile and siderophile element geochemistry. Mineralium Deposita, 45, (5), p. 443-460.

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Résumé

The Kabanga deposit constitutes one of the most significant Ni sulfide discoveries of the last two decades (indicated mineral resource 23 Mt of ore at 2.64% Ni, inferred resource 28.5 Mt at 2.7% Ni, November 2008). The sulfides are hosted by predominantly harzburgitic and orthopyroxenitic intrusions that crystallized from magnesian basaltic and picritic magmas. However, compared with other sulfide ores that segregated from such magmas (e.g., Jinchuan, Pechenga, Raglan), most Kabanga sulfides have low Ni (<1–3%), Cu (∼0.1–0.4%), and PGE contents (≪1 ppm), high Ni/Cu (5–15), and low Ni/Co (10–15) and Pd/Ir (2–20). Sulfides with higher metal contents (up to ∼5% Ni, 0.8% Cu, 10 ppm PGE) are found in only one unit from Kabanga North. The observed metal contents are consistent with segregation of magmatic sulfides from fertile to strongly metal-depleted magmas, at intermediate to very low mass ratios of silicate to sulfide liquid (R factors) of approximately 10–400. Sulfide saturation was triggered prior to final emplacement, by assimilation of up to 50% of the total sulfur in the intrusions from sulfidebearing metasedimentary country rocks. Immiscible sulfide liquid was entrained by the magma and ultimately precipitated in dynamic magma conduits that formed tubular and sill-like mafic–ultramafic bodies characterized by abundant magmatic breccias, highly irregular layering, and frequent compositional reversals. The unusually large degree of crustal contamination and the low R factors render Kabanga an end-member in the spectrum of magmatic Ni sulfide ores.

Type de document:Article publié dans une revue avec comité d'évaluation
ISSN:0026-4598
Volume:45
Numéro:5
Pages:p. 443-460
Version évaluée par les pairs:Oui
Date:2010
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
Déposé le:07 juill. 2016 15:22
Dernière modification:09 déc. 2016 16:08
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