Platinum occurs as α-PtO2 nanoparticles in deep-sea ferromanganese deposits
Abstract
Understanding how critical metals such as platinum (Pt) are enriched in marine environments is essential for advancing knowledge of their geochemical cycles and the formation of oceanic mineral resources. Pt occurs in seawater at picomolar concentrations, yet deep-sea ferromanganese (FeMn) deposits contain up to eight orders of magnitude more Pt. The mechanism behind this enrichment remains unresolved. Although FeMn deposits exhibit high Pt partitioning, their low Pt levels and the co-occurrence of multiple elements pose challenges to investigating Pt oxidation state and uptake processes using traditional spectroscopic methods. In this study, highenergy-resolution X-ray absorption spectroscopy (XAS) was used to elucidate how Pt is sequestered at the atomic scale in FeMn crusts and nodules from the Pacific, Atlantic, and Indian oceans. Pt is present in the tetravalent form, resulting from the oxidation of dissolved divalent Pt in seawater upon interaction with Mn oxides. Tetravalent Pt is precipitated as α-PtO 2 nanoparticles with longer Pt-Pt distances than in well-crystallized α-PtO 2 . Density functional theory calculations indicate that the local structure of Pt is best described by α-PtO 2 layers topotactically stacked on vernadite phyllomanganates, similar to (Co,Ni)-asbolane. The Pt content depth profiles are constant during spot analyses by laser ablation-inductively coupled plasma-mass spectrometry, suggesting that the Pt nanoparticles are uniformly dispersed within the ablated volume, rather than occurring as discrete metallic nuggets. These findings reveal a new pathway for Pt immobilization in marine environments and suggest that thermodynamically stable α-PtO 2 serves as a long-term sink for oceanic Pt. The advanced capabilities of high-energy-resolution XAS offer new opportunities to deepen understanding of how trace metals are sequestered in structurally disordered and chemically complex natural materials, with potential applications in georesource exploration.
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BibTeX
@article{liao2026platinum,
title = {{Platinum occurs as α-PtO2 nanoparticles in deep-sea ferromanganese deposits}},
author = {Jianlin Liao and Yan Li and Julien Léger and Andrea Koschinsky and Catherine Dejoie and Anne-Claire Gaillot and Irina Snigireva and Andrea Giacomelli and Stephan N. Steinmann and Olivier Mathon and Alain Manceau},
journal = {Geochimica et Cosmochimica Acta},
year = {2026},
month = sep,
doi = {10.1016/j.gca.2026.08.030},
url = {https://hal.science/hal-05762930v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Platinum occurs as α-PtO2 nanoparticles in deep-sea ferromanganese deposits
AU - Jianlin Liao
AU - Yan Li
AU - Julien Léger
AU - Andrea Koschinsky
AU - Catherine Dejoie
AU - Anne-Claire Gaillot
AU - Irina Snigireva
AU - Andrea Giacomelli
AU - Stephan N. Steinmann
AU - Olivier Mathon
AU - Alain Manceau
PY - 2026
DA - 2026/09/03
JO - Geochimica et Cosmochimica Acta
DO - 10.1016/j.gca.2026.08.030
UR - https://hal.science/hal-05762930v1
AB - Understanding how critical metals such as platinum (Pt) are enriched in marine environments is essential for advancing knowledge of their geochemical cycles and the formation of oceanic mineral resources. Pt occurs in seawater at picomolar concentrations, yet deep-sea ferromanganese (FeMn) deposits contain up to eight orders of magnitude more Pt. The mechanism behind this enrichment remains unresolved. Although FeMn deposits exhibit high Pt partitioning, their low Pt levels and the co-occurrence of multiple elements pose challenges to investigating Pt oxidation state and uptake processes using traditional spectroscopic methods. In this study, highenergy-resolution X-ray absorption spectroscopy (XAS) was used to elucidate how Pt is sequestered at the atomic scale in FeMn crusts and nodules from the Pacific, Atlantic, and Indian oceans. Pt is present in the tetravalent form, resulting from the oxidation of dissolved divalent Pt in seawater upon interaction with Mn oxides. Tetravalent Pt is precipitated as α-PtO 2 nanoparticles with longer Pt-Pt distances than in well-crystallized α-PtO 2 . Density functional theory calculations indicate that the local structure of Pt is best described by α-PtO 2 layers topotactically stacked on vernadite phyllomanganates, similar to (Co,Ni)-asbolane. The Pt content depth profiles are constant during spot analyses by laser ablation-inductively coupled plasma-mass spectrometry, suggesting that the Pt nanoparticles are uniformly dispersed within the ablated volume, rather than occurring as discrete metallic nuggets. These findings reveal a new pathway for Pt immobilization in marine environments and suggest that thermodynamically stable α-PtO 2 serves as a long-term sink for oceanic Pt. The advanced capabilities of high-energy-resolution XAS offer new opportunities to deepen understanding of how trace metals are sequestered in structurally disordered and chemically complex natural materials, with potential applications in georesource exploration.
SN - 0016-7037
SN - 1872-9533
ER -