TY - JOUR

T1 - Behavior of gold in a magma at sulfide-sulfate transition

T2 - Revisited

AU - Botcharnikov, Roman E.

AU - Holtz, Francois

AU - Mungall, James E.

AU - Beermann, Oliver

AU - Linnen, Robert L.

AU - Garbe-Schönberg, Dieter

N1 - Funding Information: This study was supported by the German Science Foundation (DFG Grants Bo2941-1 and -2) and by the Leibniz Universität Hannover. J. Feige is acknowledged for the help with the preparation of olivine containers, and T. Sisson is thanked for providing us with his data on Au concentrations in alkali-rich rocks from Hawaii. The manuscript has been substantially improved by the constructive reviews of M. Pichavant, J. Richards, C. Ballhaus, and I. Swainson. The editorial handling by I. Swainson is also greatly acknowledged. Copyright: Copyright 2013 Elsevier B.V., All rights reserved.

PY - 2013/8/1

Y1 - 2013/8/1

N2 - We have investigated experimentally the partitioning of Au between solid and liquid sulfide phases and basaltic melts at 200 MPa, at redox conditions close to the sulfide-sulfate transition, over temperatures between 1050 and 1200 °C, which span the monosulfide solid solution (MSS) - sulfide liquid (SuL) solidus. The measured MSS/basalt partition coefficient of Au (D AuMSS-sil) is about 100-200, whereas the partition coefficient of sulfide liquid/basalt (DAuSuL-sil) is approximately 10 times larger at 2200. Although we find that temperature, pressure, and oxygen fugacity (fO2) exert relatively weak controls on Au partitioning, they exert major indirect influences on Au behavior by controlling the identity of the condensed sulfide phase and by affecting S solubility. These observations have important implications for the behavior of Au in the processes of partial melting in the mantle and magma crystallization in the crust. The occurrence of natural magmas with elevated concentrations of Au and presumably other highly siderophile and chalcophile elements requires predominance of MSS over SuL in the source or/and oxidizing conditions close to or above the sulfide-sulfate transition in the magma.

AB - We have investigated experimentally the partitioning of Au between solid and liquid sulfide phases and basaltic melts at 200 MPa, at redox conditions close to the sulfide-sulfate transition, over temperatures between 1050 and 1200 °C, which span the monosulfide solid solution (MSS) - sulfide liquid (SuL) solidus. The measured MSS/basalt partition coefficient of Au (D AuMSS-sil) is about 100-200, whereas the partition coefficient of sulfide liquid/basalt (DAuSuL-sil) is approximately 10 times larger at 2200. Although we find that temperature, pressure, and oxygen fugacity (fO2) exert relatively weak controls on Au partitioning, they exert major indirect influences on Au behavior by controlling the identity of the condensed sulfide phase and by affecting S solubility. These observations have important implications for the behavior of Au in the processes of partial melting in the mantle and magma crystallization in the crust. The occurrence of natural magmas with elevated concentrations of Au and presumably other highly siderophile and chalcophile elements requires predominance of MSS over SuL in the source or/and oxidizing conditions close to or above the sulfide-sulfate transition in the magma.

KW - Basalt

KW - Enrichment

KW - Gold

KW - Magma

KW - Partitioning

KW - Solubility

KW - Sulfide

KW - Sulfur

UR - http://www.scopus.com/inward/record.url?scp=84882754681&partnerID=8YFLogxK

U2 - 10.2138/am.2013.4502

DO - 10.2138/am.2013.4502

M3 - Article

AN - SCOPUS:84882754681

VL - 98

SP - 1459

EP - 1464

JO - American Mineralogist

JF - American Mineralogist

SN - 0003-004X

IS - 8-9

ER -