Kinetic and Thermodynamic Controls on Mg and Sr Contents during Calcite Growth: Establishing a Baseline for Biological Mineralization

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Trace elements, especially those that may be used as paleoproxies, behave as lattice impurities that regulate biomineralization and provide critical information on crystal growth history. For example, incorporation of Mg2+ has been shown to modify the morphology, solubility and polymorphic expression of CaCO3 biominerals. In addition, Mg2+ is the principal inhibitor of calcite growth in natural waters, thereby influencing the size and reactivity of the biogeochemically significant carbonate reservoir. However, the fundamental mechanistic interactions of Mg2+ with calcite surfaces remain controversial. For this reason, the PI will use an experimental approach that integrates techniques from aqueous geochemistry and surface sciences to quantify the kinetic and thermodynamic controls on Mg and Sr contents of calcite grown in 0.1 M NaCl and synthetic seawater solutions. The PI also will determine the mechanism(s) by which Mg and Sr modify calcite growth properties and morphology and construct a quantitative and mechanistic model of calcite growth that provides a baseline for understanding the complexity of the influences of biological processes on the elemental composition of carbonate minerals. Results from this research will provide a baseline for understanding the influence of trace elements incorporated into calcite. This information is needed to interpret the compositions of biogenic calcite and in understanding paleotemperature data.