Experimental Determination of Equilibrium and Kinetic Fractionation of Boron, Carbon, and Oxygen Isotopes during Carbonate Precipitation

将在受控条件下评价硼、碳和氧的同位素分馏。 这些无机钙化实验的精确平衡分馏因子将提供一个共同的衡量标准，以评估生物不平衡钙化的潜在程度。 无机钙化过程中8 - 11 B、8 - 13 C和8 - 18 O分馏的同时实验分析是有吸引力的，因为最近的生物钙化理论提出了8 - 13 C和8 - 18 O的相关动力学不平衡作为钙化速率的函数。 根据这一模型，同位素不平衡产生于钙化过程中的速率依赖性无机水合和羟基化反应。 由于钙化速率在一定程度上受钙化部位溶质pH值的控制，因此对pH值敏感的8 - 11 B分馏应与 8 13 C和8 18 O动力学不平衡。 将使用pH控制的连续搅拌釜式反应器（CSTR）评价温度和沉淀速率（溶质化学）对接种无机方解石沉淀的同位素组成的影响。 在这些实验期间，将采用经XRD确认矿物学和已知同位素组成的精心选择的试剂级方解石晶种材料，以控制由于矿物学差异（例如，文石与方解石）而产生的分馏效应。

Istopic fractionation of boron, carbon and oxygen will be evaluated under controlled conditions. Accurate equilibrium fractionation factors from these inorganic calcification experiments will provide a common yardstick against which to evaluate the potential magnitude of biogenic disequilibrium calcification. Simutaneous experimental analysis of 8 11 B, 8 13 C, and 8 18 O fractionation during inorganic calcificaiton is attractive because a recent theory of biogenic calcification proposes correlated kinetic dissequilibria in 8 13 C and 8 18 O as a function of calcification rate. According to this model, isotopic disequilibrium arises from rate dependent inorganic hydration and hydroxylation reactions during calcification. Because calcification rate is controlled to some extent by solute pH at the site of calcification, 8 11 B fractionation, which is pH sensitive, should be correlated with 8 13 C, and 8 18 O kinetic disequilibrium. A pH controlled, continuously stirred tank reactor (CSTR) will be used to evaluate the effects of temperature and precipitaiton rate (solute chemistry) on the isotopic composition of seeded inorganic calcite precipitation. Carefully selected reagent grade calcite seed material with XRD confirmed mineralogy and known isotopic composition will be employed during these experiments to control for fractionation effects due to minerological differences (e.g. aragonite vs. calcite).