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The nebo-babel Ni-Cu-PGE sulfide deposit (West Musgrave, Australia) / Zoran Seat in Economic geology, Vol. 106 N° 4 (Juin/Juillet 2011) 

Public ISBD [article]  in Economic geology > Vol. 106 N° 4 (Juin/Juillet 2011) . - pp. 106-527 Titre : The nebo-babel Ni-Cu-PGE sulfide deposit (West Musgrave, Australia) : Pt. 1. U/Pb zircon ages, whole-rock and mineral chemistry, and O-Sr-Nd isotope compositions of the intrusion, with constraints on petrogenesis Type de document : texte imprimé Auteurs : Zoran Seat, Auteur ; M. A. Mary Gee, Auteur ; Benjamin A. Grguric, Auteur Année de publication : 2011 Article en page(s) : pp. 106-527 Note générale : Géologie économique Langues : Anglais (eng) Mots-clés : Nebo  babel  Sulfid  deposit  Mineral  chemistry  Intrusion  Petrogenesis Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : The Nebo-Babel intrusion, which hosts a world-class magmatic Ni-Cu-PGE sulfide deposit, is a concentrically zoned, tube-like gabbronorite body. The emplacement of Nebo-Babel at 1068.0 ± 4.3 Ma was part of a major magmatic event, which included the Giles Complex and the Warakurna large igneous province. Field, mineral, chemical, and isotopic data from the Nebo-Babel intrusion indicate that all of the lithostratigraphic units are cogenetic and that the intrusion is the product of three temporally distinct magma pulses. The initial magma pulse, which formed the marginal units of the intrusion, was the most primitive and has assimilated the highest percentage of the country-rock orthogneiss. The subsequent magma pulses, emplaced into the core of the intrusion, were both less primitive and less contaminated. The final and largest magma pulse underwent in situ closed-system crystal fractionation resulting in the observed stratigraphic mineral and whole-rock chemical trends. Emplacement of Nebo-Babel took place at ca. 10- to 12-km depth. Postmagmatic, structural overturning of the intrusion resulted in stratigraphically reversed mineral and chemical trends. All of the Nebo-Babel units can be related by crystal fractionation of parental tholeiitic magma with 8 to 9 wt percent MgO. Mineral {delta}18O values are consistent with typical mantle values and preclude large-scale crustal contamination of the parental magma with anything other than material with similar values. Although even the least contaminated intrusive units have negative Nb anomalies and enriched 87Sr/86Sr initial ratios compared to bulk earth at the time, the crustal assimilation must have been significantly less than 10 percent based on mantle-like {delta}18O values and 143Nd/144Nd ratios. Trace elements indicate that primitive Nebo-Babel melts equilibrated with spinel facies mantle implying shallow melting beneath a lithosphere less than 80 km thick. DEWEY : 553 ISSN : 0361-0128 En ligne : http://econgeol.geoscienceworld.org/cgi/content/abstract/106/4/527 [article] The nebo-babel Ni-Cu-PGE sulfide deposit (West Musgrave, Australia) : Pt. 1. U/Pb zircon ages, whole-rock and mineral chemistry, and O-Sr-Nd isotope compositions of the intrusion, with constraints on petrogenesis [texte imprimé] / Zoran Seat, Auteur ; M. A. Mary Gee, Auteur ; Benjamin A. Grguric, Auteur . - 2011 . - pp. 106-527. Géologie économique Langues : Anglais (eng) in Economic geology > Vol. 106 N° 4 (Juin/Juillet 2011) . - pp. 106-527 Mots-clés : Nebo  babel  Sulfid  deposit  Mineral  chemistry  Intrusion  Petrogenesis Index. décimale : 553 Géologie économique. Minérographie. Minéraux. Formation et gisements de minerais Résumé : The Nebo-Babel intrusion, which hosts a world-class magmatic Ni-Cu-PGE sulfide deposit, is a concentrically zoned, tube-like gabbronorite body. The emplacement of Nebo-Babel at 1068.0 ± 4.3 Ma was part of a major magmatic event, which included the Giles Complex and the Warakurna large igneous province. Field, mineral, chemical, and isotopic data from the Nebo-Babel intrusion indicate that all of the lithostratigraphic units are cogenetic and that the intrusion is the product of three temporally distinct magma pulses. The initial magma pulse, which formed the marginal units of the intrusion, was the most primitive and has assimilated the highest percentage of the country-rock orthogneiss. The subsequent magma pulses, emplaced into the core of the intrusion, were both less primitive and less contaminated. The final and largest magma pulse underwent in situ closed-system crystal fractionation resulting in the observed stratigraphic mineral and whole-rock chemical trends. Emplacement of Nebo-Babel took place at ca. 10- to 12-km depth. Postmagmatic, structural overturning of the intrusion resulted in stratigraphically reversed mineral and chemical trends. All of the Nebo-Babel units can be related by crystal fractionation of parental tholeiitic magma with 8 to 9 wt percent MgO. Mineral {delta}18O values are consistent with typical mantle values and preclude large-scale crustal contamination of the parental magma with anything other than material with similar values. Although even the least contaminated intrusive units have negative Nb anomalies and enriched 87Sr/86Sr initial ratios compared to bulk earth at the time, the crustal assimilation must have been significantly less than 10 percent based on mantle-like {delta}18O values and 143Nd/144Nd ratios. Trace elements indicate that primitive Nebo-Babel melts equilibrated with spinel facies mantle implying shallow melting beneath a lithosphere less than 80 km thick. DEWEY : 553 ISSN : 0361-0128 En ligne : http://econgeol.geoscienceworld.org/cgi/content/abstract/106/4/527