New constraints on the genesis and long-term stability of Os-rich alloys in the Earth's mantle

Fonseca, Raul O. C., Laurenz, Vera, Mallmann, Guilherme, Luguet, Ambre, Hoehne, Nadine and Jochum, Klaus Peter (2012) New constraints on the genesis and long-term stability of Os-rich alloys in the Earth's mantle. Geochimica et Cosmochimica Acta, 87 227-242. doi:10.1016/j.gca.2012.04.002


Author Fonseca, Raul O. C.
Laurenz, Vera
Mallmann, Guilherme
Luguet, Ambre
Hoehne, Nadine
Jochum, Klaus Peter
Title New constraints on the genesis and long-term stability of Os-rich alloys in the Earth's mantle
Journal name Geochimica et Cosmochimica Acta   Check publisher's open access policy
ISSN 0016-7037
1872-9533
Publication date 2012-06-15
Sub-type Article (original research)
DOI 10.1016/j.gca.2012.04.002
Volume 87
Start page 227
End page 242
Total pages 16
Place of publication Kidlington, Oxford, United Kingdom
Publisher Pergamon
Language eng
Abstract A variety of seemingly unrelated processes, such as core-mantle interaction, desulfurization, and direct precipitation from a silicate melt have been proposed to explain the formation of Ru-Os-Ir alloys (here referred to as osmiridiums) found in terrestrial mantle rocks. However, no consensus has yet been reached on how these important micrometer-sized phases form. In this paper we report the results of an experimental study on the solubilities of Ru, Os and Ir in sulfide melts (or mattes) as a function of alloy composition at 1300°C. Considering the low solubilities of Ru, Os, and Ir in silicate melts, coupled with their high matte/silicate-melt partition coefficients, our results indicate that these elements concentrate initially at the ppm level in a matte phase in the mantle source region. During partial melting, the extraction of sulfur into silicate melt leads to a decrease in fS 2 that triggers the exsolution of osmiridiums from the refractory matte in the residue. The newly formed osmiridiums may persist in the terrestrial mantle for periods exceeding billions of years.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Earth Sciences Papers
 
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