Investigation of norsethite solubility as a fundamental contribution for a better understanding of the formation of Mg-containing carbonate minerals

• Applicant: Professor Dr. Guntram Jordan
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 263836853

Dolomite [CaMg(CO3)2] is one of the most abundant carbonate minerals on Earth. The growth kinetics of dolomite at ambient temperature, however, is still not clear - laboratory syntheses in additive-free aqueous solutions fail generally. The reason for this failure is assumed to be the slow dehydration of Mg2+, which is also thought to be the reason for the growth problems of anhydrous Mg-carbonate minerals in general. Nevertheless, there is an anhydrous Mg-containing carbonate mineral which easily precipitates at room temperature from aqueous solution and which is structurally and chemically similar to dolomite: norsethite [BaMg(CO3)2]. In the BaCO3-MgCO3-system, norsethite is prevailing and occurs at variously different solution conditions and temperatures.As the solubility product of norsethite has only been determined experimentally at 25 °C, geochemical models of Ba2+ and Mg2+ containing waters at other temperatures are highly unreliable. Such models, however, are indispensable for any quantitative evaluation of mineral stability and growth kinetics at elevated temperatures. Accurate knowledge of the growth kinetics of magnesium containing minerals at elevated temperatures is of great significance (e.g., for an evaluation of the relevance of Mg-containing minerals in geological CO2 sequestration or for calculations of scale formation in industrial processes).Aim of the project, therefore, is to determine the solubility products of norsethite at various elevated temperatures (50-175 °C). These solubility products can make a significant and fundamental contribution to future carbonate mineral research. Furthermore, a comparison to the solubility product of dolomite can give valuable information to unravel the dolomite problem and to understand the easy formation of norsethite. Moreover, knowledge about norsethite growth allows a better assessment of the significance of the Mg2+ dehydration barrier during growth of Mg-containing carbonate minerals.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Wolfgang W. Schmahl