TY - JOUR

T1 - Erratic behavior of platinum-group elements along an olivine–Cr-spinel cotectic in sulfide-undersaturated basaltic magma: roles of Cr-spinel and alloys

AU - Chayka, Ivan F.

AU - Kamenetsky, Vadim S.

AU - Kutyrev, Anton V.

AU - Barnes, Sarah Jane

AU - Stepanov, Aleksandr S.

AU - Konstantinov, Sergey E.

AU - Baykov, Nikolay I.

AU - Kryazhev, Sergey G.

AU - Belousov, Ivan A.

AU - Zhukova, Irina A.

AU - Scherbakov, Vasily D.

AU - Kalugin, Valery M.

AU - Ivanov, Alexey V.

AU - Bryanskiy, Nikolay V.

AU - Park, Jung Woo

N1 - We dedicate this study to hallowed memory of our dear colleague Dmitry Varlamov, who assisted with SEM, and has unexpectedly passed away in November 2024. The authors thank Maya Kamenetsky, Karsten Goemann, Vasiliy Belyaev, Michael Khlestov, Nikolay Karmanov, Dany Savard, Audrie Lavoie and Viktoria Danilovskaya for the analytical works; Anton Nuzhdaev and Dmitry Saveliev – for the help in field works; Michael Zelensky – for an informal discussion. We thank Michael Anenburg for his thoughtful review and editor Xingcheng Liu for managing the editorial process. Vadim S. Kamenetsky in the Insititue of Oceanology, CAS, was funded by the National Natural Science Foundation of China No. W2431032. This study is a part of the research topic of the Institute of Experimental Mineralogy, Russian Academy of Sciences, project no. FMUF-2022-0004. This study was partially supported by the research topic of the IVS FEB RAS "Mineral formation in the supra-subduction zone of the North Pacific" (No. FWME-2024-0004). This study was partially supported by the DSTI-NRF Centre of Excellence (CoE) for Integrated Mineral and Energy Resource Analysis (DSTI-NRF CIMERA). Opinions expressed and conclusions arrived at, are those of the authors and are not necessarily to be attributed to the CoE. SEM investigations were partially supported by Russian Science Foundation (project number 24-77-00099). Field works and sample preparation were supported by Russian Science Foundation (project number 21-17-00122). Laser ablation ICP-MS analyses in China University of Geosciences (Wuhan) were supported by National Natural Science Foundation of China No. 42073036. Statistical modelling is done in Novosibirsk State University and partially supported by the Ministry of Science and Higher Education of the Russian Federation (project № FSUS-2020-0039).

PY - 2025/4/24

Y1 - 2025/4/24

N2 - 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.

AB - 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.

UR - https://www.mendeley.com/catalogue/7a449431-a9e9-3020-a60f-3ec8d3a17f01/

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-105003494013&origin=inward&txGid=f7ee72f7aa4b2c5071fd14a3ae215d69

U2 - 10.1038/s41598-025-97281-z

DO - 10.1038/s41598-025-97281-z

M3 - Article

C2 - 40274979

VL - 15

SP - 14366

JO - Scientific Reports

JF - Scientific Reports

SN - 2045-2322

IS - 1

M1 - 14366

ER -