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Ni-phyllosilicates (garnierites) from the Falcondo Ni-laterite deposit (Dominican Republic); mineralogy, nanotextures, and formation mechanisms by HRTEM and AEM

Cristina Villanova de Benavent, Fernando Nieto, Cecilia Viti, Joaquin A. Proenza, Salvador Gali and Josep Roque-Rosell
Ni-phyllosilicates (garnierites) from the Falcondo Ni-laterite deposit (Dominican Republic); mineralogy, nanotextures, and formation mechanisms by HRTEM and AEM
American Mineralogist (June 2016) 101 (6): 1460-1473

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 nanometer 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 (sub 001) than talc (i.e., 9.2-9.7 A), described as "kerolite"-"pimelite" in clay mineral literature.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 101
Serial Issue: 6
Title: Ni-phyllosilicates (garnierites) from the Falcondo Ni-laterite deposit (Dominican Republic); mineralogy, nanotextures, and formation mechanisms by HRTEM and AEM
Affiliation: Universitat de Barcelona, Facultat de Geologia, Barcelona, Spain
Pages: 1460-1473
Published: 201606
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 55
Accession Number: 2016-079207
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
N17°30'00" - N20°00'00", W72°00'00" - W68°19'60"
Secondary Affiliation: Universidad de Granada, ESP, SpainUniversita degli Studi di Siena, ITA, ItalyLawrence Berkeley National Laboratory, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201638
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