The elemental and isotopic fractionation of lithium between inorganic calcite and aqueous solutions has been measured as a function of solution chemistry in mixed CaCl₂-NaHCO₃ aqueous solutions spanning a range of pH from ~6 to ~9.5 at room temperature. Vaterite added to the solution recrystallized to calcite with limited change in solution chemistry. With this experimental design solution pH and Na/Ca strongly correlate. The ratio of the concentration of Li in the calcite to that of the solution (K_d,Li = [Li]_calcite/[Li]_solution), increased by about an order of magnitude with increasing pH. The Li exchange coefficient (K_d,Li/Ca=([Li]_calcite/[Ca]_calcite)/([Li]_solution/[Ca]_solution) decreased by about four orders of magnitude, from ~10⁻² to ~10⁻⁶ with increasing pH due to the large decrease in solution Ca content with increasing experiment pH. The Li isotope fractionation also changed systematically as the pH of the solution increased from 6.5 to 9.5 with the calcite ranging from about −6‰ to +2‰ relative to the solution it grew from. No change in either the elemental or isotopic partitioning was observed with either a change in the Li concentration of the solution or with a change in the experimental duration (5–400 days). To better understand the role of diffusive Li isotope fractionation a series of experiments were performed to determine the relative diffusivity of ⁶Li and ⁷Li in solutions with different pH. The results suggest little or no difference in relative diffusivity (D_6Li ~ 0.998D_7Li) across the range of solution chemistry considered (pH 4 to ~7.5). The change in Li partitioning between calcite and solution with changing solution chemistry is consistent with Li incorporation into calcite as LiHCO₃ and hence a dependence on solution H⁺/Ca²⁺. If this interpretation is correct, it means that the concentration of Li in inorganic calcite precipitated from seawater at fixed Ca and Li concentrations will increase with decreasing pH. The change in the Li isotope fractionation factor with changing solution chemistry may either reflect a kinetic isotope fractionation associated with changing calcite growth rates or a change in the equilibrium fractionation factor due to changing Li speciation in the solution. These results, while not directly applicable to pristine biogenic calcite, have important implications for interpreting the Li content of calcite that has undergone any diagenetic modification (e.g., all bulk carbonate Li isotope data). Diagenesis under variable conditions provides a plausible alternative explanation for Li isotope excursions in carbonate sediment sequences that have been interpreted as indicating changing seawater δ⁷Li that deserves further investigation.

无机方解石和水溶液之间锂的元素和同位素分馏已作为溶液化学的函数在混合 CaCl ₂ -NaHCO ₃水溶液中测量，pH 范围在室温下从 ~6 到 ~9.5。添加到溶液中的球霰石重结晶为方解石，溶液化学变化有限。有了这个实验设计溶液，pH 值和 Na/Ca 强烈相关。方解石中 Li 的浓度与溶液中 Li 的浓度之比（K _d,Li  = [Li]_方解石/[Li]_溶液），随着 pH 值的增加而增加了大约一个数量级。Li交换系数(K _d,Li/Ca =([Li]_方解石/[Ca]_方解石)/([Li]_溶液/[Ca]_溶液) 减少了大约四个数量级，从 ~10 ^-2到 ~10 ^-6随着 pH 值的增加，由于溶液 Ca 含量随着实验 pH 值的增加而大幅下降。随着溶液的 pH 值从 6.5 增加到 9.5，Li 同位素分馏也发生了系统性变化，方解石相对于其生长的溶液的范围从约 -6‰ 到 +2‰。随着溶液中锂浓度的变化或实验持续时间（5-400 天）的变化，没有观察到元素或同位素分配的变化。为了更好地理解扩散 Li 同位素分馏的作用，进行了一系列实验以确定⁶ Li 和⁷ Li 在不同 pH 值的溶液中的相对扩散率。结果表明相对扩散率差异很小或没有差异 (D _6Li  ~ 0.998D_7Li ) 在所考虑的溶液化学范围内 (pH 4 至 ~7.5)。随着溶液化学性质的变化，锂在方解石和溶液之间分配的变化与锂以 LiHCO _{3 的形式}掺入方解石一致，因此依赖于溶液 H ⁺ /Ca ²⁺. 如果这种解释是正确的，则意味着在固定的 Ca 和 Li 浓度下，从海水中沉淀出的无机方解石中的 Li 浓度将随着 pH 值的降低而增加。Li同位素分馏因子随溶液化学性质的变化而变化，可能反映了与方解石生长速率变化相关的动力学同位素分馏，或者由于溶液中锂形态的变化而引起的平衡分馏因子的变化。这些结果虽然不能直接适用于原始生物成因方解石，但对于解释经过任何成岩改造的方解石的锂含量（例如，所有大块碳酸盐锂同位素数据）具有重要意义。⁷值得进一步调查的李。