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Title: Fibrous platinum-group minerals in 'floating chromitites' from the Loma Larga Ni-laterite deposit, Dominican Republic
Author: Aiglsperger, Thomas Hans
Proenza Fernández, Joaquín Antonio
Longo, Francisco
Font Bardia, Ma. Mercedes
Galí Medina, Salvador, 1949-
Roqué, Josep
Baurier Aymat, Sandra
Keywords: Fibres tèxtils
República Dominicana
Meteorització química
Textile fibers
Dominican Republic
Chemical weathering
Issue Date: 30-Nov-2016
Publisher: MDPI
Abstract: This contribution reports on the observation of enigmatic fibrous platinum-group minerals (PGM) found within a chromitite body included in limonite ("floating chromitite") from Ni-laterites in the Dominican Republic. Fibrous PGM have a Ru-Os-Ir-Fe dominated composition and are characterized by fibrous textures explained by grain-forming fibers which are significantly longer (1-5 µm) than they are wide (~100 nm). Back-scattered electron (BSE) images suggest that these nanofibers are platinum-group elements (PGE)-bearing and form <5 µm thick layers of bundles which are oriented orthogonal to grains' surfaces. Trace amounts of Si are most likely associated with PGE-bearing nanofibers. One characteristic fibrous PGM was studied in detail: XRD analyses point to ruthenian hexaferrum. However, the unpolished fibrous PGM shows numerous complex textures on its surface which are suggestive for neoformation processes: (i) features suggesting growth of PGE-bearing nanofibers; (ii) occurrence of PGM nanoparticles within film material (biofilm?) associated with PGE-bearing nanofibers; (iii) a Si-rich and crater-like texture hosting PGM nanoparticles and an Ir-rich accumulation of irregular shape; (iv) complex PGM nanoparticles with ragged morphologies, resembling sponge spicules and (v) oval forms (<1 µm in diameter) with included PGM nanoparticles, similar to those observed in experiments with PGE-reducing bacteria. Fibrous PGM found in the limonite may have formed due to supergene (bio-)weathering of fibrous Mg-silicates which were incorporated into desulphurized laurite during stages of serpentinization.
Note: Reproducció del document publicat a:
It is part of: Minerals, 2016, vol. 6, num. 4, p. 126
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ISSN: 2075-163X
Appears in Collections:Articles publicats en revistes (Mineralogia, Petrologia i Geologia Aplicada)

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