Élodie Muller's PhD | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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Early and present Geobiosphere

  Élodie Muller's PhD

Deconvolution of the sulfur cycle in Archean sulfate deposits using quadruple sulfur isotope (32S, 33S, 34S, 36S) analyses
Encadrant (et co-encadrant) : 
Résumé: 
Aggregates of zoned pyrites in a 3.2 Gy old black chert from Barberton (South Africa).

Archean sulfate deposits are restricted to a few barite deposits in Western Australia, India and South Africa. These deposits formed episodically between 3.5 and 3.2 Ga ago and are associated with felsic volcanoclastic sediments. It has been showed that the sulfates and associated sulfides from Australia and South Africa define a negative trend in a mass dependent (MDF; δ34S) vs mass independent (MIF; ∆33S) fractionation diagram. This trend has been attributed to an episode of intense release of volcanic SO2 into the atmosphere. In addition, many pyrites in barite deposits show strongly negative δ34S values that can be attributed to a MDF sulfur isotope effect caused by sulfur disproportionation or sulfate-reduction. In order to better understand the sulfur cycle associated with the formation of the barite deposits we performed a 4-S-isotope study of the samples from Australia and South Africa previously investigated for their 3 sulfur isotopes as well as new samples from India.