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

微量元素，特别是那些可能被用作古替代物的元素，表现为晶格杂质，调节生物矿化，并提供关于晶体生长历史的关键信息。例如，镁离子的掺入已经被证明改变了CaCO3生物矿物的形态、溶解度和多晶性表达。此外，镁离子是天然水体中方解石生长的主要抑制因素，从而影响具有生物地球化学意义的碳酸盐岩储层的大小和反应性。然而，镁离子与方解石表面的基本机制相互作用仍然存在争议。为此，PI将使用一种综合了水中地球化学和表面科学技术的实验方法来量化在0.1M氯化钠和合成海水溶液中生长的方解石的镁和锶含量的动力学和热力学控制。等电点还将确定镁和锶改变方解石生长性质和形貌的机理(S)，并建立方解石生长的定量和机理模型，为理解生物过程对碳酸盐矿物元素组成影响的复杂性提供基线。这项研究的结果将为了解方解石中掺入的微量元素的影响提供基线。这些信息对于解释生物源方解石的成分和理解古温度数据是必要的。

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.