Séminaire ISTerre

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Shedding new light on the dolomite problem

mercredi 7 décembre 2022 - 10h00

Carlos Pimentel - ISTerre-Séminaire Post-doc (Café croissant à 9h45)
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Dolomite, CaMg(CO3)2, is an ubiquitous mineral in the Earth’s crust and the second most abundant carbonate after calcite, CaCO3. Since its first description by Deodat Gratet de Dolomieu at the end of the XVIII century, dolomite has attracted the interest of mineralogists. What is the reason for this scientific attraction? Because, at present, this mineral does not seem to extensively crystallize in the geological environments where, assumedly, it had been formed in the past, i.e. sedimentary environments at temperatures lower than 100 ºC. During Holocene, dolomite has only precipitated in very restricted natural environments, e.g. sabkhas, speleothems in caves and saline or hypersaline lakes. In addition, in laboratory experiments, dolomite has not yet been synthesized at temperatures below 100 ºC. This apparent impossibility to synthesize dolomite in the laboratory (T < 100 ºC) and the scarce number of Holocene dolomites are the main basis of one of the most longstanding mineralogical question, i.e. the so-called “dolomite problem”. In this seminar, I will present the results obtained on the synthesis at ambient temperature of dolomite analogues (i.e., BaMg(CO3)2, named norsethite, and PbMg(CO3)2) and on the theoretical structures of dolomite analogues studied by using first principle calculations. These results will be discussed from their implications to the dolomite formation. In addition, the results on the study of natural dolomite structures of different geological ages will be also presented. All these results will be used to shed light on the dolomite problem.

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Equipe organisatrice : Organisation labo

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères