Erratic behavior of platinum-group elements along an olivine–Cr-spinel cotectic in sulfide-undersaturated basaltic magma: roles of Cr-spinel and alloys
The behavior of platinum-group elements (PGE) in sulfide-undersaturated primitive magmas may be controlled by crystallization of either Cr-spinel, platinum-group minerals (PGM) or olivine. Evaluation of the PGM-hosted PGE portion is challenging because PGM in volcanic rocks are small and rare. We report on the sizes and compositions of PGM associated with Cr-spinel, the PGE content of Cr-spinel and olivine, and the bulk rock PGE content from sulfide undersaturated arc volcanics of the Tumrok range (Eastern Kamchatka). Platinum-iron and Ir-Os alloys (< 30 to > 3000 nm in size) form inclusions in Cr-spinel. Their presence and composition are mostly independent of Cr-spinel chemistry. Bulk rock PGE contents are erratic and PGE concentrations in Cr-spinel are exceptionally variable (up to 2 orders of magnitude). Whereas PGM inclusions in Cr-spinel and PGE in solid solution in Cr-spinel significantly contribute to the bulk rock PGE budget, a considerable portion of the PGE must be present associated with minerals other than Cr-spinel. The variable PGE content of the rocks is attributed to a combination of: (a) disequilibrium kinetic effects at the Cr-spinel-melt boundary layer, strongly affecting PGE partitioning into Cr-spinel and crystallization of PGM in the layer; (b) the presence of some sufficiently large PGM to cause nugget effects; and (c) melt degassing.
Authors
- S. G. Kryazhev (ORCID: https://orcid.org/0000-0002-9845-0661)
- Nikolay I. Baykov
- V. D. Scherbakov
- V. M. Kalugin
- Ivan F. Chayka (ORCID: https://orcid.org/0000-0001-7222-8600)
- Vadim S. Kamenetsky (ORCID: https://orcid.org/0000-0002-2734-8790)
- S. G. Konstantinov
- Stephen J. Barnes (ORCID: https://orcid.org/0000-0002-4912-9177)
- Anton V. Kutyrev (ORCID: https://orcid.org/0000-0001-5933-6455)
- Nikolay V. Bryanskiy (ORCID: https://orcid.org/0000-0002-9132-5446)
- Ivan A. Belousov (ORCID: https://orcid.org/0000-0002-9224-6408)
- I Zhukova (ORCID: https://orcid.org/0000-0003-2725-9285)
- Jung‐Woo Park (ORCID: https://orcid.org/0000-0002-3792-451X)
- Alexey V. Ivanov
- A.S. Stepanov
Institutions
- Université du Québec à Chicoutimi (CA)
- University of Tasmania (AU)
- Seoul National University (KR)
- Novosibirsk State University (RU)
- University of the Witwatersrand (ZA)
- Lomonosov Moscow State University (RU)
- China University of Geosciences (CN)
- Institute of Experimental Mineralogy (RU)
- Central Research Institute of Geological Prospecting for Base and Precious Metals (RU)
- Siberian Branch of the Russian Academy of Sciences (RU)
- Budker Institute of Nuclear Physics (RU)
Publication Details
- Journal
- Scientific Reports
- Published
- 2025-04-24
- DOI
- https://doi.org/10.1038/s41598-025-97281-z
- Citations
- 2
- Primary Topic
- Geological and Geochemical Analysis
- Type
- article
- Field-Weighted Citation Impact
- 3.73
Funders
- National Natural Science Foundation of China
- Far East Branch, Russian Academy of Sciences
- Russian Science Foundation
- Ministry of Science and Higher Education of the Russian Federation
- China University of Geosciences
- DSI-NRF Centre of Excellence for Integrated Mineral and Energy Resource Analysis
- Russian Academy of Sciences