Isotopic responses of magnesium to two types of dissolution-reprecipitation processes for the growth of the double-carbonate mineral norsethite

Abstract

An important mechanism of carbonate mineral growth is dissolution-reprecipitation, including the transformation of amorphous precursor to crystalline carbonates, and coarsening (ripening) of fine carbonate crystals. However, the mechanistic details of cation exchange associated with carbonate mineral growth via a dissolution-reprecipitation process are still not well understood. In this study, we used Mg isotopes to probe the exchange of Mg between aqueous solutions and norsethite [BaMg(CO 3 ) 2 ] by systematic synthesis experiments. Norsethite is a model double carbonate, with a general formula of AB(CO 3 ) 2 , where A and B stand for two different divalent ions. Formation of norsethite comprised of three stages, including 1) precipitation of barium-magnesium amorphous carbonate, 2) transformation of This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America.The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.