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GEOREF RECORD

Origin of noble-metal nuggets in sulfide-saturated arc magmas; a case study of olivine-hosted sulfide melt inclusions from the Tolbachik Volcano (Kamchatka, Russia)

Vadim S. Kamenetsky and Michael Zelenski
Origin of noble-metal nuggets in sulfide-saturated arc magmas; a case study of olivine-hosted sulfide melt inclusions from the Tolbachik Volcano (Kamchatka, Russia)
Geology (Boulder) (April 2020) 48 (6): 620-624

Abstract

Minerals that contain platinum-group elements (PGEs) and occur in some magmatic Cu-Ni sulfide deposits have been ascribed to crystallization from an originally PGE-rich sulfide liquid. The occurrence of PGE-bearing minerals (PGMs) in some sulfide-undersaturated primitive melts has been envisaged and recently reported, whereas direct crystallization of PGMs in sulfide-saturated silicate magmas is seemingly hindered by strong partitioning of PGE into immiscible sulfide melts. In this study, we discovered abundant nanoparticles containing noble metals in association with sulfide melt inclusions entrapped inside primitive olivine phenocrysts (Fo85-92) from the recent basaltic magma of the Tolbachik volcano (Kamchatka arc, Russia). These nuggets occur in swarms on the surface of the sulfide globules and are represented by native metals, sulfides, and alloys of Pd, Pt, Au, Pb, and Bi. The nuggets on different globules can be either Pd- or Pt-rich nuggets, and the compositions are highly variable, even among adjacent nuggets. We argue that the diffusive supply of Pd from the external nuggets can be responsible for significant uptake of Pd (up to 2 wt%) in the sulfide melt. We consider direct crystallization of PGMs in a primitive basaltic melt undergoing sulfide unmixing, and possibly sulfide breakdown due to oxidation, as another mechanism additional to their "classic" origin from the PGE-rich sulfide melt in response to solidification.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 48
Serial Issue: 6
Title: Origin of noble-metal nuggets in sulfide-saturated arc magmas; a case study of olivine-hosted sulfide melt inclusions from the Tolbachik Volcano (Kamchatka, Russia)
Affiliation: University of Tasmania, School of Natural Sciences, Hobart, Tasmania, Australia
Pages: 620-624
Published: 20200413
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 24
Accession Number: 2020-039367
Categories: Economic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2020195
Illustration Description: illus.
N55°49'60" - N55°49'60", E160°19'60" - E160°19'60"
Secondary Affiliation: Russian Academy of Sciences, Institute of Experimental Mineralogy, RUS, Russian Federation
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 202025
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