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XAS evidence for Ni sequestration by siderite in a lateritic Ni-deposit from New Caledonia

Gabrielle Dublet, Farid Juillot, Guillaume Morin, Emmanuel Fritsch, Vincent Noel, Jessica Brest and Gordon E. Brown
XAS evidence for Ni sequestration by siderite in a lateritic Ni-deposit from New Caledonia
American Mineralogist (January 2014) 99 (1): 225-234


Mineralogical and spectroscopic analyses were conducted on a lateritic Ni-deposit from Southern New Caledonia. Results show that Ni is incorporated in siderite (FeCO (sub 3) ) found between 37 and 40 m depth in the laterite and saprolite units of the regolith. SEM-EDXS analyses of siderite-rich samples indicate that a significant amount of nickel can be hosted by this crystalline phase ( approximately 0.8 wt% NiO). Ni and Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopic analyses of the siderite-rich samples from the regolith as well as comparison with synthetic Ni-bearing and Ni-free siderites demonstrate isomorphous substitution of Ni (super 2+) for Fe (super 2+) in the siderite structure. Linear combination fitting (LCF) of the Ni K-edge EXAFS data reveals that this Ni-bearing siderite species accounts for more than 90% of the total Ni pool (1 wt% NiO) in the siderite-rich horizons of the regolith. In addition, LCF analysis of the EXAFS spectra indicates that goethite and serpentine are the major Ni hosts in the upper horizons (laterite) and lower horizons (saprolite) of the regolith, respectively. Formation of siderite, an uncommon mineral species in such oxidized environments, is attributed to the development of swampy conditions in organic-rich lateritic materials that accumulated at the bottom of dolines. These results thus show the importance of siderite as a host for nickel in lateritic Ni deposits that have been affected by late hydromorphic and reducing conditions.

ISSN: 0003-004X
EISSN: 1945-3027
Serial Title: American Mineralogist
Serial Volume: 99
Serial Issue: 1
Title: XAS evidence for Ni sequestration by siderite in a lateritic Ni-deposit from New Caledonia
Affiliation: Universite Pierre et Marie Curie, Institut de Mineralogie et de Physique des Milieux Condenses, Paris, France
Pages: 225-234
Published: 201401
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 68
Accession Number: 2014-008055
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
S22°30'00" - S20°00'00", E164°00'00" - E167°00'00"
Secondary Affiliation: Stanford University, 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: 201406
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