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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
Petrogenesis of Archean PGM-bearing chromitites and associated ultramafic-mafic-anorthositic rocks from the Guelb el Azib layered complex (West African craton, Mauritania)
Precambrian Research, Volume 224, Year 2013
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Description
The Archean Guelb el Azib layered complex (GAC) in the West African craton of Mauritania is composed of an association of serpentinites, chromitites, amphibolites and anorthosites with few fine-grained amphibolite dykes. The complex forms tectonic slices in 2.9-3.5. Ga TTG gneiss terrains in close association with supracrustal rocks (BIFs, impure marbles, amphibolites). It was affected by a main granulite-facies grade metamorphism (up to 900. °C at 5-6. kbar) with subsequent retrogression in amphibolite and greenschist facies conditions. The preserved igneous macrostructures, the mineral compositions and the nature of relic magmatic assemblages have been used to constrain the composition of the parental melts and the conditions of crystallization. According to petrological observations and to comparison with experimental data, the formation of the complex can be explained by fractionation of a slightly hydrous high-alumina basaltic melt at low pressure. The early fractionation of olivine and the absence of massive clinopyroxene fractionation before plagioclase saturation led to crystallization of highly calcic plagioclase with Fe-, Al-rich but Cr-poor chromite from a hydrous tholeiitic parental magma, similar to worldwide Archean tholeiites. The complex shares many similarities with Archean anorthosite layered complexes, possibly formed in a supra-subduction zone environment according to results obtained on similar 2.9-3.0. Ga complexes from Greenland and India (namely Fiskenaesset and Sittampundi). Three phases of PGE mineralization affected the GAC chromitites: (i) igneous crystallization of laurite; (ii) formation of late magmatic IPGE sulpho-arsenides (irarsite-hollingworthite) and (iii) hydrothermal Pt-Pd mineralization represented by sperrylite and rustenburgite. © 2012 Elsevier B.V.
Authors & Co-Authors
Berger, Julien L.R.
Belgium, Brussels
Université Libre de Bruxelles
Diot, Hervé
France, Nantes
Nantes Université
Lô, Khalidou
Mauritania, Nouakchott
University of Nouakchott Université de Nouakchott
Ohnenstetter, Daniel
France, Paris
Cnrs Centre National de la Recherche Scientifique
Féménias, Olivier
Canada, Toronto
Iamgold Corporation
Pivin, Marjorie
Belgium, Brussels
Université Libre de Bruxelles
Demaiffe, Daniel
Belgium, Brussels
Université Libre de Bruxelles
Bernard, Alain
Belgium, Brussels
Université Libre de Bruxelles
Charlier, Bernard
United States, Cambridge
Massachusetts Institute of Technology
Statistics
Citations: 9
Authors: 9
Affiliations: 6
Identifiers
Doi:
10.1016/j.precamres.2012.10.005
ISSN:
03019268
Study Approach
Qualitative
Study Locations
Mauritania