TY - JOUR

T1 - High gold concentrations in sulphide-bearing magma under oxidizing conditions

AU - Botcharnikov, Roman E.

AU - Linnen, Robert L.

AU - Wilke, Max

AU - Holtz, Francois

AU - Jugo, Pedro J.

AU - Berndt, Jasper

N1 - Funding Information: We thank O. Diedrich for the preparation of samples for analysis. We thank J. Susini, M. Salomé and M. Cotte from Beamline ID21 at the ESRF for their expertise and assistance during collection of the XANES data. B. Fryer and Z. Yang from Great Lakes Institute for Environmental Research, University of Windsor, Canada are acknowledged for the help with LA-ICP-MS measurements of glasses. The German Science Foundation (DFG; Project Bo2941) and the Natural Science and Engineering Research Council of Canada are acknowledged for the financial support. Copyright: Copyright 2011 Elsevier B.V., All rights reserved.

PY - 2011/2

Y1 - 2011/2

N2 - Magmas are an important source of noble metals. Metals are transported by magma from deep within the mantle to the shallow crust, where they form subsurface ore deposits1-6. The concentration of noble metals in silicate melts has been thought to be controlled by the stability of sulphide minerals in the upper mantle and crust, with only sulphide-undersaturated magmas capable of extracting significant amounts of metals from the mantle 1-6. Here we present a series of experiments carried out on basaltic and andesitic glasses, melted in the presence of water and sulphur in gold capsules at a pressure of 200 MPa and a temperature of 1,050 °C, under a wide range of redox conditions. We show that gold solubility in silicate melts is highest within a narrow window of redox conditions, characterized by the transformation of sulphide to sulphate species in the magma. Within this redox range, we found that gold was particularly mobile and became dissolved in the silicate melts as a sulphide-bearing component. We suggest that gold-rich magmas can be generated in mantle systems that are sulphide-saturated, as long as they are relatively oxidized. Conditions that are favourable to the mobilization and transport of gold (and presumably other noble metals) may prevail in magmatic systems above subduction zones and in the environments beneath hotspot volcanoes.

AB - Magmas are an important source of noble metals. Metals are transported by magma from deep within the mantle to the shallow crust, where they form subsurface ore deposits1-6. The concentration of noble metals in silicate melts has been thought to be controlled by the stability of sulphide minerals in the upper mantle and crust, with only sulphide-undersaturated magmas capable of extracting significant amounts of metals from the mantle 1-6. Here we present a series of experiments carried out on basaltic and andesitic glasses, melted in the presence of water and sulphur in gold capsules at a pressure of 200 MPa and a temperature of 1,050 °C, under a wide range of redox conditions. We show that gold solubility in silicate melts is highest within a narrow window of redox conditions, characterized by the transformation of sulphide to sulphate species in the magma. Within this redox range, we found that gold was particularly mobile and became dissolved in the silicate melts as a sulphide-bearing component. We suggest that gold-rich magmas can be generated in mantle systems that are sulphide-saturated, as long as they are relatively oxidized. Conditions that are favourable to the mobilization and transport of gold (and presumably other noble metals) may prevail in magmatic systems above subduction zones and in the environments beneath hotspot volcanoes.

UR - http://www.scopus.com/inward/record.url?scp=79551611500&partnerID=8YFLogxK

U2 - 10.1038/ngeo1042

DO - 10.1038/ngeo1042

M3 - Article

AN - SCOPUS:79551611500

VL - 4

SP - 112

EP - 115

JO - Nature Geoscience

JF - Nature Geoscience

SN - 1752-0894

IS - 2

ER -