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X-ray photoelectron spectroscopy characterization of natural chromite from Mercedita Mine (eastern Cuba); quantification of the Fe (super 3+) /Fe (super 2+) ratio

Isabel Fanlo, Fernando Gervilla, Ester Mateo and Silvia Irusta
X-ray photoelectron spectroscopy characterization of natural chromite from Mercedita Mine (eastern Cuba); quantification of the Fe (super 3+) /Fe (super 2+) ratio
European Journal of Mineralogy (February 2008) 20 (1): 125-129

Abstract

The quantitative estimation of the Fe (super 3+) /Fe (super 2+) ratio has a crucial interest to know the upper-mantle oxidation state. The relative proportions of Fe (super 3+) and Fe (super 2+) are usually estimated from electron microprobe analysis (EPMA) assuming chromite stoichiometry. In order to test a new technique to estimate the Fe (super 3+) /Fe (super 2+) ratio and to avoid EPMA systematic errors, X-ray photoelectron spectroscopy (XPS) has been used to determine the Fe (super 3+) /Fe (super 2+) ratio in four chromite samples from Cuba and the results compared with those obtained by EPMA. Due to the high surface sensitivity of XPS the samples were etched by removing the outermost layers by bombarding with an Ar (super +) ion gun. Therefore, the surface, as well as 8, 16 and 24 nm in-depth levels, were analyzed, revealing that the spectra change significantly with depth. Thus, from the surface down to 24 nm deep, Fe (super 3+) concentrations decrease from values up to 10 at.% to values below the detection limit of XPS (0.1 at.%). By contrast, a systematic Fe (super 3+) detection (between 1.32 and 4.04 at.%) was observed by EPMA. Consequently, XPS allows us to calculate ferric iron contents, a key datum for the calculation of the real structural formula of chromite. XPS can therefore be considered a useful tool in evaluating mantle oxidation state.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 20
Serial Issue: 1
Title: X-ray photoelectron spectroscopy characterization of natural chromite from Mercedita Mine (eastern Cuba); quantification of the Fe (super 3+) /Fe (super 2+) ratio
Affiliation: Universidad de Zaragoza, Departmento Ciencias de la Tierra, Saragossa, Spain
Pages: 125-129
Published: 200802
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 27
Accession Number: 2008-072094
Categories: General geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
N19°49'60" - N23°15'00", W85°00'00" - W74°00'00"
Secondary Affiliation: CSIC-Universidad de Granada, ESP, Spain
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200819
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