Metal recycling tracked by mercury and helium isotopes in platinum–palladium nuggets from Córrego Bom Sucesso, Brazil

Metal recycling tracked by mercury and helium isotopes in platinum–palladium nuggets from Córrego Bom Sucesso, Brazil

The enigmatic botryoidal nuggets of platinum (Pt) and palladium (Pd) from Córrego Bom Sucesso in the southern Serra do Espinhaço, Minas Gerais, Brazil, are considered to have formed during supergene alteration of placer deposits. This requires hitherto unidentified precious-metal enrichment processe...

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Veröffentlicht in:Chemical geology 2022-03, Vol.593, p.120752, Article 120752
Hauptverfasser: Cabral, Alexandre Raphael, Deng, Changzhou, Yin, Runsheng, Yakubovich, Olga V., Stuart, Finlay M., Tupinambá, Miguel, Lehmann, Bernd
Format: Artikel
Sprache:eng
Schlagworte:
Brazil
Córrego Bom Sucesso
Helium isotopes
Mercury isotopes
Minas Gerais
Platinum–palladium nuggets
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Zusammenfassung:The enigmatic botryoidal nuggets of platinum (Pt) and palladium (Pd) from Córrego Bom Sucesso in the southern Serra do Espinhaço, Minas Gerais, Brazil, are considered to have formed during supergene alteration of placer deposits. This requires hitherto unidentified precious-metal enrichment processes and is inconsistent with Pt–Os age of 180 Ma that entails formation at depth, as recently proposed. Here we report the first mercury (Hg) and helium (He) isotopic determinations of Pt–Pd nuggets. Mercury isotopic compositions have a mass-independent fractionation (MIF) signature with an odd-mass deficit (Δ199Hg = − 0.22 ± 0.04; 1SD, n = 15), which requires aqueous photochemical reduction of Hg (II). Extremely low 3He/4He (
ISSN:0009-2541
1872-6836
DOI:10.1016/j.chemgeo.2022.120752