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Chemistry of iron sulfides in sedimentary environments

Rickard, David, Schoonen, M.A.A. and Luther, G.W. 1995. Chemistry of iron sulfides in sedimentary environments. Presented at: Symposium on Geochemical Transformations of Sedimentary Sulfur, at the 208th National Meeting of the American Chemical Society, Washington, DC, USA, 21-25 August 1994. Published in: Vairavamurthy, M.A. and Schoonen, M.A.A. eds. Geochemical Transformations of Sedimentary Sulfur. pp. 168-193.

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Abstract

Recent advances in understanding the chemistry of iron sulfides in sedimentary environments are beginning to shed more light on the processes involved in the global sulfur cycle. Pyrite may be formed via at least three routes including the reaction of precursor sulfides with polysulfides, the progressive solid-state oxidation of precursor iron sulfides and the oxidation of iron sulfides by hydrogen sulfide. The kinetics and mechanism of the polysulfide pathway are established and those of the H2S oxidation pathway are being investigated. Preliminary considerations suggest that the relative rates of the three pathways are H2S oxidation > polysulfide pathway much greater than solid-state oxidation. The kinetics and mechanisms of iron(II) monosulfide formation suggest the involvement of iron bisulfide complexes in the pathway and iron bisulfide complexes have now been identified by voltammetry and their stabililty constants measured. The framboidal texture commonly displayed by sedimentary pyrite appears to be an extreme example of mosaicity in crystal growth. Framboidal pyrite is produced through the H2S oxidation reaction. Frontier molecular orbital calculations are beginning to provide theoretical underpinning of the reaction mechanisms. Recent progress in understanding iron sulfide chemistry is leading to questions regarding the degree of involvement of precursor iron sulfides in the formation of pyrite in sediments. Spin-offs from the work are addressing problems relating to the involvement of iron sulfides in the origin of life, the nature of metastability, the mechanism of precipitation reactions and the use of iron sulfides in advanced materials.

Item Type: Conference or Workshop Item (Paper)
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Last Modified: 27 Feb 2019 16:37
URI: http://orca.cf.ac.uk/id/eprint/119969

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