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The tectonomagmatic source of ore metals and volatile elements in the southern kermadec arc / R. J. Wysoczanski in Economic geology, Vol. 107 N° 8 (Décembre 2012) 

Public ISBD [article]  in Economic geology > Vol. 107 N° 8 (Décembre 2012) . - pp. 1539-1556 Titre : The tectonomagmatic source of ore metals and volatile elements in the southern kermadec arc Type de document : texte imprimé Auteurs : R. J. Wysoczanski, Auteur ; M. R. Handler, Auteur ; C. I. Schipper, Auteur Année de publication : 2013 Article en page(s) : pp. 1539-1556 Note générale : economic geology Langues : Anglais (eng) Mots-clés : chalcophile  metals;  volatile  elements Résumé : Deciphering the ultimate source of chalcophile metals (e.g., Cu, Zn, Pb) in volcanogenic massive sulfide (VMS) deposits and the volatiles that help drive their formation is critical for understanding where, how, and why VMS deposits form. The southern Kermadec arc volcanic front is known to be highly hydrothermally active and host to at least three VMS deposits, whereas the associated back -arc system is apparently hydrothermally inactive, although this may simply be due to a lack of exploration in this region. We have analyzed major, trace, and volatile element concentrations in a suite of basaltic glasses and olivine-hosted melt inclusions from volcanoes, ridges, and rifts of the southern Kermadec arc volcanic front and Havre Trough back-arc basin. These data indicate clear compositional differences in the mantle beneath the arc front and the back arc, with the arc front having higher extents of prior melt extraction and enrichment in volatile and metal elements from slab-derived aqueous fluids. The magmatic budget of Pb is supplied to the mantle source by these slab-derived fluids, whereas magmatic concentrations of Zn and Cu are primarily controlled by the degree of partial melting, with a Cu-bearing residual phase required in the mantle. Consequently, the relative enrichment of chalcophile metals in the mantle-derived melts is Pb >> Cu > Zn. The magma volatile history recorded by the glasses and melt inclusions indicates that degassing during crystal fractionation is significant and, notably, leads to the reduction of sulfur in the evolving magma as oxidized sulfur degasses preferentially. The apparent absence (or retention) of volatiles (notably CO2 and SO3) in magma chambers, lack of magmatic activity, and absence of hot, mafic dikes beneath volcanoes may be important factors in inhibiting the formation of active hydrothermal venting, and by extension the potential for VMS deposition. DEWEY : 553 ISSN : 0361-0128 En ligne : http://econgeol.geoscienceworld.org/content/107/8/1539.short [article] The tectonomagmatic source of ore metals and volatile elements in the southern kermadec arc [texte imprimé] / R. J. Wysoczanski, Auteur ; M. R. Handler, Auteur ; C. I. Schipper, Auteur . - 2013 . - pp. 1539-1556. economic geology Langues : Anglais (eng) in Economic geology > Vol. 107 N° 8 (Décembre 2012) . - pp. 1539-1556 Mots-clés : chalcophile  metals;  volatile  elements Résumé : Deciphering the ultimate source of chalcophile metals (e.g., Cu, Zn, Pb) in volcanogenic massive sulfide (VMS) deposits and the volatiles that help drive their formation is critical for understanding where, how, and why VMS deposits form. The southern Kermadec arc volcanic front is known to be highly hydrothermally active and host to at least three VMS deposits, whereas the associated back -arc system is apparently hydrothermally inactive, although this may simply be due to a lack of exploration in this region. We have analyzed major, trace, and volatile element concentrations in a suite of basaltic glasses and olivine-hosted melt inclusions from volcanoes, ridges, and rifts of the southern Kermadec arc volcanic front and Havre Trough back-arc basin. These data indicate clear compositional differences in the mantle beneath the arc front and the back arc, with the arc front having higher extents of prior melt extraction and enrichment in volatile and metal elements from slab-derived aqueous fluids. The magmatic budget of Pb is supplied to the mantle source by these slab-derived fluids, whereas magmatic concentrations of Zn and Cu are primarily controlled by the degree of partial melting, with a Cu-bearing residual phase required in the mantle. Consequently, the relative enrichment of chalcophile metals in the mantle-derived melts is Pb >> Cu > Zn. The magma volatile history recorded by the glasses and melt inclusions indicates that degassing during crystal fractionation is significant and, notably, leads to the reduction of sulfur in the evolving magma as oxidized sulfur degasses preferentially. The apparent absence (or retention) of volatiles (notably CO2 and SO3) in magma chambers, lack of magmatic activity, and absence of hot, mafic dikes beneath volcanoes may be important factors in inhibiting the formation of active hydrothermal venting, and by extension the potential for VMS deposition. DEWEY : 553 ISSN : 0361-0128 En ligne : http://econgeol.geoscienceworld.org/content/107/8/1539.short