Rhodium Solubility in Silicate Melts

All published experimental data on Rh solubility in silicate melts were combined to derive an equation relating Rh solubility to temperature, oxygen fugacity, and a melt composition. It is demonstrated that Rh is dissolved in a melt dominantly as Rh 2+ in the entire experimental f O 2 range, from pu...

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Bibliographic Details
Published in:Petrology 2022-08, Vol.30 (4), p.429-438
Main Author: Borisov, A. A.
Format: Article
Language:English
Subjects:
Coefficients
Earth and Environmental Science
Earth mantle
Earth Sciences
Fayalite
Fugacity
Geochemistry
Heavy metals
Iron silicates
Magnetite
Melts
Metals
Mineralogy
Minerals
Noble metals
Oxygen
Rhodium
Rocks
Silicates
Solubility
Temperature
Temperature dependence
Upper mantle
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Summary:All published experimental data on Rh solubility in silicate melts were combined to derive an equation relating Rh solubility to temperature, oxygen fugacity, and a melt composition. It is demonstrated that Rh is dissolved in a melt dominantly as Rh 2+ in the entire experimental f O 2 range, from pure oxygen to QFM + 2 (QFM is the quartz–magnetite–fayalite buffer). The temperature dependence of Rh solubility is anomalous. Similar to the solubilities of other noble metals, Rh solubility at a constant f O 2 increases with increasing temperature. The Rh metal/silicate partition coefficient was calculated ( ≈ 3.5 × 10 7 ) for the expected conditions of Earth differentiation into a core and mantle. It is demonstrated that the late chondritic veneer model is able to best explain high Rh contents in upper mantle rocks. The suggested equation makes it possible to discard experimental glasses contaminated with metallic Rh micronuggets and thus to get rid of at least the most gross errors in the determination of Rh partition coefficients between rock-forming minerals and melt.
ISSN:0869-5911
1556-2085
DOI:10.1134/S0869591122030031