The accumulation of Ni in serpentines and garnierites from the Falcondo Ni-laterite deposit (Dominican Republic) elucidated by means of μXAS
| Autor: | Joaquín A. Proenza, Cristina Villanova-de-Benavent, Josep Roqué-Rosell |
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| Rok vydání: | 2017 |
| Předmět: |
Mineral
Chemical weathering 010504 meteorology & atmospheric sciences República Dominicana Metallurgy Dominican Republic Geochemistry chemistry.chemical_element engineering.material Saprolite 010502 geochemistry & geophysics 01 natural sciences Garnierite Nickel chemistry.chemical_compound chemistry Geochemistry and Petrology engineering Laterite Meteorització química Chemical composition Geology 0105 earth and related environmental sciences EMPA Solid solution |
| Zdroj: | Dipòsit Digital de la UB Universidad de Barcelona |
| Popis: | 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 Fe 2+ 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 Fe 3+ . 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. |
| Databáze: | OpenAIRE |
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