The accumulation of Ni in serpentines and garnierites from the Falcondo Ni-laterite deposit (Dominican Republic) elucidated by means of μXAS

Ni-bearing serpentines and garnierites (Ni-bearing Mg-phyllosilicates) are the main Ni ores in the Falcondo Ni-laterite deposit (Dominican Republic). In the present paper a set of garnierite samples and the associated Ni-bearing serpentines with characteristic mineral compositions and textures, from the saprolite horizon, were studied by EMPA, μXRF and μXAS. The ultimate goal is to elucidate, for the first time, the Fe speciation and the Ni local environment of saprolite ores from Ni-laterites of the Dominican Republic. The chemical composition of the minerals has been obtained by means of EMPA and the Ni, Fe and Cr elemental maps obtained by μXRF allowed distinguishing the saprolite fragments containing Ni-bearing serpentines and Fe oxyhydroxides from the garnierite veins. The Fe K-edge μXANES demonstrated that Fe in the Ni-poor primary serpentine is mostly in the Fe2+ form, whereas in the Ni-bearing serpentine constituting the bulk of the saprolite and in the Fe-bearing garnierite Type I Fe was in the form of Fe3+. In parallel, the local environment of Ni determined by means of Ni K-edge μEXAFS confirmed that in Ni-poor primary serpentines Ni formed a homogeneous Ni-Mg solid solution, in garnierites formed Ni-Ni clusters, and in Ni-bearing secondary serpentines Ni was found in Ni-Mg and Ni-Ni mixed sites. This paper explains the accumulation of Ni, the speciation of Fe in garnierites with various mineral compositions and in Ni-bearing serpentines from the saprolite horizon in Ni-laterite deposits

Mineralogía, composición y procesos formadores de filosilicatos de Ni en lateritas niquelíferas (serpentina-Ni y garnieritas): EMP, MET y espectroscopía Raman

Los depósitos de lateritas niquelíferas contienen importantes reservas de Ni, y recientemente han superado a los sulfuros magmáticos como la principal fuente de este metal (McRae, 2018). Además, actualmente están siendo considerados como posibles fuentes no convencionales de elementos críticos como cobalto, escandio y elementos del grupo del platino (EGP) (Aiglsperger et al., 2016

Reactive transport modelling: the formation of Ni-laterite profiles (Punta Gorda, Moa Bay, Cuba).

Ni-laterites represent one of the main Ni sources worldwide, with about 40% of the annual production (Gleeson et al.,2003). The Punta Gorda Ni laterite deposit is part of a larger province of nickel laterites in northeast Cuba (Moa Bay district) (Lavaut, 1998) developed from serpentinized peridotites

Talc- and serpentine-like 'garnierites' from Falcondo Ni-laterite deposit (Dominican Republic): a HRTEM approach

"Garnierites" represent significant Ni ore minerals in the lower horizons of many Ni-laterite deposits worldwide (e.g. Freyssinet et al., 2005). They consist of a green, fine-grained mixture of hydrous i-bearing magnesium phyllosilicates, including serpentine, talc, sepiolite, smectite and chlorite (e.g. Brindley and Hang, 1973; Springer, 1974; Brindley et al., 1979). Thus, "garnierite" is a general descriptive term and is not recognized as a mineral species by the IMA Commission on New Mineral and Mineral Names (CNMMN). For this reason, "garnierites" have been classified as "serpentine-", "talc-" and "clay-like garnierites", respectively (e.g. Brindley and Maksimovic, 1974)

Reactive transport model of the formation of oxide-type Ni-laterite profiles (Punta Gorda, Moa Bay, Cuba)

Oxide-type Ni-laterite deposits are characterized by a dominant limonite zone with goethite as the economically most important Ni ore mineral and a thin zone of hydrous Mg silicate-rich saprolite beneath the magnesium discontinuity. Fe, less soluble, is mainly retained forming goethite, while Ni is redeposited at greater depth in a Fe(III) and Ni-rich serpentine (serpentine II) or in goethite, where it adsorbs or substitutes for Fe in the mineral structure. Here, a 1D reactive transport model, using CrunchFlow, of Punta Gorda oxide-type Ni-laterite deposit (Moa Bay, Cuba) formation is presented. The model reproduces the formation of the different laterite horizons in the profile from an initial, partially serpentinized peridotite, in 10(6) years, validating the conceptual model of the formation of this kind of deposits in which a narrow saprolite horizon rich in Ni-bearing serpentine is formed above peridotite parent rock and a thick limonite horizon is formed over saprolite. Results also confirm that sorption of Ni onto goethite can explain the weight percent of Ni found in the Moa goethite.Sensitivity analyses accounting for the effect of key parameters (composition, dissolution rate, carbonate concentration, quartz precipitation) on the model results are also presented. It is found that aqueous carbonate concentration and quartz precipitation significantly affects the laterization process rate, while the effect of the composition of secondary serpentine or of mineral dissolution rates is minor. The results of this reactive transport modeling have proven useful to validate the conceptual models derived from field observations

Ni-enrichment processes revealed by TEM imaging on garnierites

Ni-phyllosilicates, commonly grouped under the name of "garnierites", are significant nickel ores found in hydrous silicate-type Ni-laterite deposits worldwide. They usually occur as vein infillings in the lower parts of laterite profiles, and consist of fine-grained, often intimately mixed, nickelmagnesium phyllosilicates, including serpentine, talc, sepiolite, smectite and chlorite (e.g. Brindley & Maksimović, 1974)

Ni-bearing phyllosilicates ('garnierites'): New insights from thermal analysis, μRaman and IR spectroscopy.

Ni-Mg-phyllosilicates, so-called 'garnierites', are significant Ni ores in Ni-laterite deposits worldwide. In addition, they are the natural analogues of synthetic catalysts involving Ni and phyllosilicate substrates used in reactions for the remediation of greenhouse gases. However, the nomenclature, classification and characterisation of Ni-Mg-phyllosilicates is a long-lasting problem, because of their fine-grained nature, poor crystallinity and frequent occurrence as intimate mixtures. This work presents and discusses DTA-TG, Raman and FTIR spectroscopy data of a series of well characterised, naturally occurring Ni-Mg-phyllosilicate samples with a variety of mineral compositions (including serpentine-dominated, talc-dominated and sepiolite-falcondoite, with various Ni contents). The results are compared to data obtained from crystalline, 1:1 and 2:1Mg-phyllosilicates and from the literature. DTA-TG confirmed that the talc-like fraction in garnierite mixtures belongs to the kerolite-pimelite series. The different garnierite types analysed are distinguishable from their Raman and FTIR spectra, and the serpentine, talc and sepiolite components could be identified (e.g. by Raman bands at ~690cm⁠−1, ~670cm⁠−1 and ~200cm⁠−1, respectively). Knowledge of Raman and FTIR vibrations of garnierites with constrained structure and composition is paramount in order to effectively characterise these phyllosilicates, and can be applied to mineral identification in ore exploration and processing, and after synthesis for nanotechnology purposes

Micro-Raman spectroscopy of garnierite minerals: a useful method for phase identification

Garnierites are important Ni-Ores found in worldwide hydrous silicate-type Ni-laterites

Dissolution kinetics of Ni-phyllosilicates from the Falcondo Deposit, Dominican Republic

Ni-phyllosilicates, commonly grouped under the name of "garnierites", are significant nickel ores found in hydrous silicate-type Ni-laterite deposits worldwide, formed by weathering of ultramafic rocks. Garnierites consist of one or more fine-grained nickelmagnesium phyllosilicates, including serpentine, talc, sepiolite, smectite and chlorite. They often occur as poorly crystalline micron-scale mixtures (e.g. Brindley, 1978)

Mineralogy and geochemistry of Fe-Ti oxide ores from the Don Dieguito massif type anorthosite suite, Sierra Nevada de Santa Marta, Colombia

Fe-Ti oxide ores are commonly associated with Proterozoic massif-type anorthosite bodies emplaced during the Grenville orogeny (~1.2-1.0 Ga). Some of these anorthositic bodies occur in the northernmost part of the Santa Marta Massif, Colombia. They locally contain crosscutting Fe-Ti(-V) ore bodies between the El Hierro creek and the Don Dieguito river. We have distinguished two types of Fe-Ti(-V) ores: i) oxide-apatite norite (fine grained ilmenite and magnetite disseminated in an assemblage of apatite, amphibole, chlorite, rutile and sericitized plagioclase) and ii) banded nelsonite (coarser grained ilmenite, magnetite and apatite distributed in bands, with minor baddeleyite, srilankite and högbomite)