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Mineralogical evolution of Fe-Si-rich layers at the olivine-water interface during carbonation reactions

Giuseppe D. Saldi, Damien Daval, Hua Guo, Francois Guyot, Sylvain Bernard, Corentin Le Guillou, James A. Davis and Kevin G. Knauss
Mineralogical evolution of Fe-Si-rich layers at the olivine-water interface during carbonation reactions
American Mineralogist (December 2015) 100 (11-12): 2655-2669

Abstract

Recent studies investigating carbonation of iron-bearing silicates have shown that the rates of these reactions, although formally not depending on oxygen fugacity, are strongly different at different redox states of the system (Saldi et al. 2013; Sissmann et al. 2013). Here we provide a micro- and nanostructural characterization of the olivine/water interface during the carbonation of forsteritic olivine at 150 degrees C and p (sub CO2) =100 bar. When the reaction starts under oxic conditions, the observed temporal sequence of interfacial layers consists of: a hematite/SiO (sub 2(am)) assemblage, Fe-rich phyllosilicates with mixed Fe valence and a non-passivating Fe-free amorphous SiO (sub 2) layer, which allows the formation of ferroan magnesite. In contrast, starting at micro-oxic conditions, carbonation rates are much faster, with no real evidence of interfacial layers. Separate deposits of goethite/lepidocrocite in the early stages of the reaction and then formation of magnetite are observed at these conditions, while precipitation of siderite/magnesite proceeds unhindered. The evolution of the redox conditions during the reaction progress controls the sequence of the observed reaction products and the passivating properties of Fe-Si-rich interfacial layers. These findings have important implications for modeling the carbonation of ultramafic rocks under different oxygen fugacity conditions as well as for understanding the technological implications of adding accessory gases to CO (sub 2) in carbon capture and storage mineralization processes involving ultrabasic rocks.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 100
Serial Issue: 11-12
Title: Mineralogical evolution of Fe-Si-rich layers at the olivine-water interface during carbonation reactions
Affiliation: Lawrence Berkeley National Laboratory, Earth Sciences Division, Berkeley, CA, United States
Pages: 2655-2669
Published: 201512
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 73
Accession Number: 2016-007454
Categories: General mineralogy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
Secondary Affiliation: Universite de Strasbourg, FRA, FranceSorbonne Universites, FRA, France
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 201604
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