ORCID Profile
0000-0001-8120-2939
Current Organisation
Université du Québec à Chicoutimi
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Publisher: Society of Economic Geologists
Date: 15-02-2012
Publisher: Elsevier BV
Date: 2014
Publisher: Springer Science and Business Media LLC
Date: 07-2009
DOI: 10.1038/NATURE08205
Publisher: Society of Economic Geologists, Inc.
Date: 08-2013
DOI: 10.2113/ECONGEO.108.5.953
Abstract: The Kunene Complex of Namibia-Angola is one of the largest anorthosite massifs on Earth (up to 18,000 km2), consisting of several distinct anorthosite and leucotroctolite intrusions. The Namibian portion of the Kunene Complex measures ~80 × 50 km, ~4,000 km2, and is dominated by the Zebra Mountain lobe, a ~16-km-thick dome-like mass of interlayered, relatively unaltered dark leucotroctolite with relatively altered, “white,” anorthosite. Past studies and the present work have found evidence for intrusion of two distinct phases of dark leucotroctolite into the white anorthosite, namely a relatively early, deformed, phase dated at 1363 ± 17 Ma (U-Pb in baddelyite), and a relatively later and undeformed phase whose absolute age remains unknown. The Kunene leucotroctolites are among the least evolved troctolites known from anorthosite complexes, with olivine containing 59 to 77 mol % forsterite and up to 1,700 ppm Ni, and plagioclase containing 56 to 69 mol % anorthosite. Our isotope data from the troctolites indicate a relatively small crustal component (δ18O, ~5.3–7.3 δ34S, 0.5–1 and ɛNdT, 0.9–1.8), whereas Nd and oxygen isotope data from the white anorthosites, published by other workers, showed a slightly larger crustal component (e.g., ɛNdT as low as −3 δ18O up to 7.5‰). In the periphery of the Kunene Complex are several, relatively small (& km2), mafic-ultramafic intrusions comprising peridotite, pyroxenite, gabbro, troctolite, and anorthosite. Some of these bodies are Ni-Cu-PGE mineralized, including the Ohamaremba troctolite, the Oncocua pyroxenite, and the Ombuku peridotite-gabbronorite. The latter additionally contains a massive chromitite layer. A new U-Pb baddelyite age of 1220 ± 15 Ma for Ohamaremba indicates that the latter postdates the main Kunene Complex by ~140 Ma. The relative enrichment in MgO, Cr, and Ni, and the O, Nd, and S isotope characteristics of Kunene magmatism suggest that the primary magmas were predominantly mantle-derived picrites or basalts. The massif-type anorthosites formed through ascent of feldspathic slurries followed by downward draining of residual liquid. Subsequent magma pulses formed troctolitic sills within the anorthosite plutons and mafic-ultramafic satellite intrusions in the periphery of the anorthosites. The recurring nature of Kunene mafic-ultramafic magmatism results from several successive mantle upwellings. Partial mantle melts ascended through reactivated translithospheric lineaments along the southern margin of the Congo craton.
Publisher: Mineralogical Society
Date: 13-04-2018
DOI: 10.1180/MINMAG.2017.081.100
Abstract: Post-magmatic alteration of certain magmatic Ni sulfide ores in Western Australia, the Miitel deposit and the Sarah's Find prospect, produced Ni–As–PGE haloes around massive sulfides. A study of the composition of arsenide grains from these hydrothermal haloes, along with arsenides from various magmatic and hydrothermal mineralized environments in other localities, was conducted in order to compare their composition, and assess their potential use as indicator minerals for exploration vectoring, as well as to gain knowledge on their crystallization history. Concentrations in trace elements such as platinum-group elements (PGEs), Au and other metals was obtained by laser ablation inductively coupled plasma mass spectroscopy analyses. Results show that variations in PGEs and Au compositions can be related to the magmatic vs. hydrothermal origin of the grains and to their provenance from deposits enriched in either Ni, Au or both. Magmatic NiCoFe sulfarsenides have strongly correlated, high IPGE (Os, Ir, Ru, Rh) contents up to 100 ppm Ir, compared with maximum values in hydrothermal sulfarsenides of ~1 ppm. Gold in hydrothermal sulfarsenides from Au-mineralized ultramafic rocks extends up to 500 ppm, with typical values of 3–30 ppm similar values are also found in nickeline (also called niccolite). These results suggest that nickel arsenides could potentially be used as indicator minerals for nickel and gold exploration. Trace-element contents of arsenide grains in shear zones could be used to deduce the presence of Ni or Au mineralization upstream in the fluid pathway.
Publisher: Springer Science and Business Media LLC
Date: 19-07-1996
Publisher: Springer Science and Business Media LLC
Date: 16-08-2007
Publisher: Elsevier BV
Date: 03-2009
Publisher: Elsevier BV
Date: 03-2019
Publisher: Oxford University Press (OUP)
Date: 23-04-2013
Publisher: Mineralogical Association of Canada
Date: 09-2017
Publisher: Elsevier BV
Date: 04-2012
Publisher: Geological Society of America
Date: 12-2010
DOI: 10.1130/G31265.1
No related grants have been discovered for Sarah-Jane Barnes.