Please use this identifier to cite or link to this item: https://hdl.handle.net/2445/163122
Title: Supergene neoformation of Pt-Ir-Fe-Ni alloys: multistage grains explains nugget formation in Ni-laterites
Author: Aiglsperger, Thomas Hans
Proenza Fernández, Joaquín Antonio
Font Bardia, Ma. Mercedes
Baurier Aymat, Sandra
Galí Medina, Salvador, 1949-
Lewis, J. F.
Longo, Francisco
Keywords: Nitrats
Platí
Minerals de platí
República Dominicana
Nitrates
Platinum
Platinum ores
Dominican Republic
Issue Date: Feb-2017
Publisher: Springer Verlag
Abstract: Ni-laterites from the Dominican Republic host rare but extremely platinum-group element (PGE)-rich chromitites (up to 17.5 ppm) without economic significance. These chromitites occur either included in saprolite (beneath the Mg discontinuity) or as 'floating chromitites' within limonite (above the Mg discontinuity). Both chromitite types have similar iridium-group PGE (IPGE)-enriched chondrite normalized patterns; however, chromitites included in limonite show a pronounced positive Pt anomaly. Investigation of heavy mineral concentrates, obtained via hydroseparation techniques, led to the discovery of multistage PGE grains: (i) Os-Ru-Fe-(Ir) grains of porous appearance are overgrown by (ii) Ni-Fe-Ir and Ir-Fe-Ni-(Pt) phases which are overgrown by (iii) Pt-Ir-Fe-Ni mineral phases. Whereas Ir-dominated overgrowths prevail in chromitites from the saprolite, Pt-dominated overgrowths are observed within floating chromitites. The following formation model for multistage PGE grains is discussed: (i) hypogene platinum-group minerals (PGM) (e.g. laurite) are transformed to secondary PGM by desulphurization during serpentinization; (ii) at the stages of serpentinization and/or at the early stages of lateritization, Ir is mobilized and recrystallizes on porous surfaces of secondary PGM (serving as a natural catalyst) and (iii) at the late stages of lateritization, biogenic mediated neoformation (and accumulation) of Pt-Ir-Fe-Ni nanoparticles occurs. The evidence presented in this work demonstrates that in situ growth of Pt-Ir-Fe-Ni alloy nuggets of isometric symmetry is possible within Ni-laterites from the Dominican Republic.
Note: Versió postprint del document publicat a: https://doi.org/10.1007/s00126-016-0692-6
It is part of: Mineralium Deposita, 2017, vol. 52, num. 7, p. 1069-1083
URI: https://hdl.handle.net/2445/163122
Related resource: https://doi.org/10.1007/s00126-016-0692-6
ISSN: 0026-4598
Appears in Collections:Articles publicats en revistes (Mineralogia, Petrologia i Geologia Aplicada)

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