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Distribution of Te, As, Bi, Sb, and Se in mid-ocean ridge basalt and komatiites and in picrites and basalts from large igneous provinces: Implications for the formation of magmatic Ni-Cu-platinum group element deposits

Barnes Sarah-Jane et Mansur Eduardo T.. (2022). Distribution of Te, As, Bi, Sb, and Se in mid-ocean ridge basalt and komatiites and in picrites and basalts from large igneous provinces: Implications for the formation of magmatic Ni-Cu-platinum group element deposits. Economic Geology, 117, (8), p. 1919-1933.

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URL officielle: http://dx.doi.org/doi.org/10.5382/econgeo.4887

Résumé

In magmatic nickel-copper-platinum-group element (PGE) deposits, the PGEs are found both in solid solution in base metal sulfides and as platinum group minerals (PGMs). Apart from S, the most common elements that the PGEs combine with to form PGMs are Te, As, Bi, Sb, and Sn (TABS). Whether the TABS play a role in collecting the PGEs or simply partition into the sulfide liquid along with the PGEs and later combine with PGEs when the sulfide phase becomes saturated with PGMs is not currently clear. This is in part because the concentrations of TABS in the magmas (picrites and basalts from large igneous province and komatiites) that form these types of deposits are not well established, and hence it is not evident whether the magmas contain sufficient TABS to control PGEs. In order to establish the concentrations of Te, As, Bi, Sb, and Se (TABS+) in these rock types and to document the processes affecting these concentrations, we have determined TABS+ concentrations in komatiites, in mid-ocean ridge basalt, and in picrites and basalts from large igneous provinces. Using TABS+ mantle-normalized diagrams, the affects of different mantle sources, crystal fractionation, crustal assimilation, degassing, and alteration are considered. We estimate the concentrations of TABS+ in komatiites to be approximately twice primitive mantle values. In picrites the concentrations vary: approximately 10 times primitive mantle values for As and Sb and decreasing through Bi to Te from 7 to 2 times primitive mantle.

Assimilation of S-bearing sedimentary rocks is thought to be important in triggering sulfide saturation leading to the formation of Ni-Cu-PGE deposits. Assimilation of such sediments would enrich the magma in Th over Nb and in As, Sb, and Bi. Evidence of assimilation in the form of TABS and Th enrichment is clear in the PGE reef deposits of the Bushveld and Stillwater Complexes, but the deposits do not contain sufficient TABS to control the PGEs. This is also true in the Norilsk-Talnakh Ni-Cu-PGE deposits. However, at Norilsk degassing of the magma has resulted in the loss of TABS, which results in negative As, Bi, Se, and Te anomalies on primitive mantle-normalized plots.

Type de document:Article publié dans une revue avec comité d'évaluation
ISSN:0361-0128
Volume:117
Numéro:8
Pages:p. 1919-1933
Version évaluée par les pairs:Oui
Date:2022
Identifiant unique:10.5382/econgeo.4887
Sujets:Sciences naturelles et génie > Génie
Sciences naturelles et génie > Sciences appliquées
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:tellurium, arsenic, antinomy, selenium, bismuth, platinum-group elements, magmatic ore deposits, crustal assimilation; sulfide segregation; degassing, Siberian flood basalts, komatiites, MORB, Karoo, Etendeka, Emeishan, tellure, antinomie, sélénium, éléments du groupe du platine, gisements de minerai magmatique, assimilation crustale, ségrégation des sulfures, dégazage, basaltes d'inondation sibérienne
Déposé le:28 janv. 2023 17:32
Dernière modification:09 févr. 2023 15:33
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