Aiglsperger, Thomas HansProenza Fernández, Joaquín AntonioLongo, FranciscoFont Bardia, Ma. MercedesGalí Medina, Salvador, 1949-Roqué, JosepBaurier Aymat, Sandra2020-03-022020-03-022016-11-302075-163Xhttps://hdl.handle.net/2445/151708This 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.11 p.application/pdfengcc-by (c) Aiglsperger, Thomas Hans et al., 2016http://creativecommons.org/licenses/by/3.0/esFibres tèxtilsRepública DominicanaMeteorització químicaTextile fibersDominican RepublicChemical weatheringinfo:eu-repo/semantics/article6655082020-03-02info:eu-repo/semantics/openAccess