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Title: Ni-phyllosilicates (garnierites) from the Falcondo Ni-laterite deposit (Dominican Republic): Mineralogy, nanotextures, and formation mechanisms by HRTEM and AEM
Author: Villanova de Benavent, Cristina
Nieto, Fernando
Viti, Cecilia
Proenza Fernández, Joaquín Antonio
Galí Medina, Salvador, 1949-
Roqué, Josep
Keywords: Níquel
República Dominicana
Dominican Republic
Issue Date: 1-May-2016
Publisher: Mineralogical Society of America
Abstract: Ni-bearing magnesium phyllosilicates (garnierites) are significant Ni ores in Ni-laterites worldwide. The present paper reports a detailed TEM investigation of garnierites from the Falcondo Ni-laterite deposit (Dominican Republic). Different types of garnierites have been recognized, usually consisting of mixtures between serpentine and talc-like phases that display a wide range of textures at the nano meter scale. In particular, chrysotile tubes, polygonal serpentine, and lizardite lamellae are intergrown with less crystalline, talc-like lamellae. Samples consisting uniquely of talc-like and of sepiolite-falcondoite were also observed, occurring as distinctive thin lamellae and long ribbon-shaped fibers, respectively. HRTEM imaging indicates that serpentine is replaced by the talc-like phase, whereas TEM-AEM data show preferential concentration of Ni in the talc-like phase. We suggest, therefore, that the crystallization of Ni-bearing phyllosilicates is associated with an increase in the silica activity of the system, promoting the replacement of the Ni-poor serpentine by the Ni-enriched talc-like phase. These results have interesting implications in material science, as garnierites are natural analogs of Ni-bearing phyllosilicate-supported synthetic catalysts. Finally, SAED and HRTEM suggest that the Ni-bearing talc-like phase corresponds to a variety of talc with extra water, showing larger d(001) than talc (i.e., 9.2-9.7 angstrom), described as 'kerolite'-'pimelite' in clay mineral literature.
Note: Versió postprint del document publicat a:
It is part of: American Mineralogist, 2016, vol. 101, num. 6, p. 1460-1473
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ISSN: 0003-004X
Appears in Collections:Articles publicats en revistes (Mineralogia, Petrologia i Geologia Aplicada)

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