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Alkali metals control the release of gold from volatile-rich magmas

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Zajacz, Z and Seo, JH and Candela, PA and Piccoli, PM and Heinrich, CA and Guillong, M (2010) Alkali metals control the release of gold from volatile-rich magmas. Earth and Planetary Science Letters, 297 (1-2). pp. 50-56. ISSN 0012-821X

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Abstract

Magmatic-hydrothermal ore deposits are a major resource of gold. Volatiles exsolving from magmas rising through the Earth's crust are the key agent for enrichment of gold in these deposits. We report the first experimental determination of gold solubilities in the magmatic volatile phases at conditions typical of most magmas associated with gold deposits (T = 1000 degrees C, P = 150 MPa). We show that gold hydrosulfide complexes supersede gold chloride complexes, and more importantly, that the stability of gold hydrosulfide complexes is greatly increased by the presence of minute concentrations of KC or NaCl (0.1-0.5 mol/kg H2O). The amplifying effect of alkali chlorides on the solubility of gold in H2S bearing volatiles may explain the preferential association of many giant hydrothermal gold deposits with high-potassium alkaline mafic to intermediate igneous rocks, which exsolve volatiles that simultaneously contain both H2S and alkali chlorides in significant concentrations. (C) 2010 Elsevier B.V. All rights reserved.

Item Type: Article
Journal or Publication Title: Earth and Planetary Science Letters
Page Range: pp. 50-56
ISSN: 0012-821X
Identification Number - DOI: 10.1016/j.epsl.2010.06.002
Additional Information: The definitive version is available at http://www.sciencedirect.com
Date Deposited: 08 Dec 2010 02:19
Last Modified: 18 Nov 2014 04:15
URI: http://eprints.utas.edu.au/id/eprint/10458
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