A Combined Model for Kinetic Clumped Isotope Effects in the CaCO 3 ‐DIC‐H 2 O System
A Combined Model for Kinetic Clumped Isotope Effects in the CaCO 3 ‐DIC‐H 2 O System
复制标题
CaCO 3 -DIC -H 2 O 系统中动力学团块同位素效应的组合模型
DOI：
10.1029/2021gc010200
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Devriendt, Laurent S.
中科院分区：
文献类型：
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作者：
Watkins, James M.;Devriendt, Laurent S.
大多数地球表面碳酸盐沉淀出与其宿主溶液的同位素平衡，使稳定同位素在古环境重建中的应用变得复杂。不平衡可由DIC-H2O系统中的交换反应以及DIC-CaCO 3系统中的晶体生长反应引起。现有的模型占动力学同位素效应（KIEs）在这些系统中分别，但模型尚未结合在一个通用的框架。在这里，开发了一个开放系统箱模型，用于描述CaCO 3-DIC-H2O系统中的不平衡碳，氧和聚集（Δ47，Δ48和Δ49）同位素效应。该模型被用来模拟方解石沉淀实验中的CO2和CaCO 3的通量和同位素组成的约束。使用平衡和动力学分馏因子的文献汇编，方解石的模拟δ 18 O和Δ 47值与涵盖晶体生长速率和溶液pH的宽范围的实验数据吻合良好。珊瑚，有孔虫，和高pH值藻）或脱气（例如，洞穴沉积物、低pH碳酸盐和低温碳酸盐）和/或与其它溶解的无机碳源混合。
Most Earth surface carbonates precipitate out of isotopic equilibrium with their host solution, complicating the use of stable isotopes in paleoenvironment reconstructions. Disequilibrium can arise from exchange reactions in the DIC‐H2O system as well as during crystal growth reactions in the DIC‐CaCO3system. Existing models account for kinetic isotope effects (KIEs) in these systems separately but the models have yet to be combined in a general framework. Here, an open‐system box model is developed for describing disequilibrium carbon, oxygen, and clumped (Δ47, Δ48, and Δ49) isotope effects in the CaCO3‐DIC‐H2O system. The model is used to simulate calcite precipitation experiments in which the fluxes and isotopic compositions of CO2and CaCO3were constrained. Using a literature compilation of equilibrium and kinetic fractionation factors, modeledδ18O and Δ47values of calcite are in good agreement with the experimental data covering a wide range in crystal growth rate and solution pH. This relatively straightforward example provides a foundation for adapting the model to other situations involving CO2absorption (e.g., corals, foraminifera, and high‐pH travertines) or degassing (e.g., speleothems, low‐pH travertines, and cryogenic carbonates) and/or mixing with other dissolved inorganic carbon sources.