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Crystallization of platinum-group minerals from silicate melts: evidence from Cr-spinel–hosted inclusions in volcanic rocks


Kamenetsky, VS and Park, J-W and Mungall, JE and Pushkarev, EV and Ivanov, AV and Kamenetsky, MB and Yaxley, GM, Crystallization of platinum-group minerals from silicate melts: evidence from Cr-spinel-hosted inclusions in volcanic rocks, Geology, 43, (10) pp. 903-906. ISSN 0091-7613 (2015) [Refereed Article]

Copyright Statement

© 2015 Geological Society of America.

DOI: doi:10.1130/G37052.1


The formation of platinum-group minerals (PGM) during magma differentiation has been suggested to be an important process in primitive magma evolution, but decisive textural evidence is difficult to obtain because PGM tend to be very small and very rare. We have investigated Cr-spinel phenocrysts from two oxidized magmas (Siberian meimechite and Vanuatu [Ambae Island] arc picrite) and one reduced magma (Uralian [Russia] ankaramite) for PGM inclusions and their platinum-group element (PGE) contents. We observed Os-Ir and Pt-Fe alloys entrapped as inclusions in Cr-spinel in all three suites of lava. The alloys may occur in association with PGE-bearing sulfides and co-trapped silicate melt. Cr-spinel crystals also contain measurable amounts of Os, Ir, Ru, and Rh, which are at concentrations 2×–100× higher than mantle values. Thermodynamic models indicate that the arc picrite and ankaramite melts were probably both saturated with the observed PGM phases, whereas the Os-Ir alloy grain observed in the meimechite is not in equilibrium with the "bulk" melt. Our results demonstrate that PGM (alloys and sulfides) occur as liquidus phases in primitive (unfractionated) melts at high temperature and at a variety of redox conditions, and that Cr-spinel is a significant host of PGE, either in the crystal structure or as PGM inclusions.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Geology
Research Field:Igneous and metamorphic petrology
Objective Division:Mineral Resources (Excl. Energy Resources)
Objective Group:Mineral exploration
Objective Field:Precious (noble) metal ore exploration
UTAS Author:Kamenetsky, VS (Professor Vadim Kamenetsky)
UTAS Author:Kamenetsky, MB (Dr Maya Kamenetsky)
ID Code:104294
Year Published:2015
Funding Support:Australian Research Council (DP130100257)
Web of Science® Times Cited:45
Deposited By:Earth Sciences
Deposited On:2015-11-07
Last Modified:2017-10-30

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