COAD Box Model

Description

This repository contains MATLAB scripts to compute the δ¹³C, δ¹⁸O, Δ₄₇, Δ₄₈, and Δ₄₉ of calcite precipitated from a CO₂-fed solution. The full description of the model and parameters can be found in: Watkins, J. and Devriendt, L. 2022, A combined model for kinetic clumped isotope effects in the CaCO₃-DIC-H₂O system, submitted to Geochemistry, Geophysics, Geosystems.

If you use these codes, I recommend that you also cite the following papers:

1. Watkins, J.M. and Hunt, J.D., 2015. A process-based model for non-equilibrium clumped isotope effects in carbonates. Earth and Planetary Science Letters, 432, pp.152-165.
2. Chen, S., Gagnon, A.C. and Adkins, J.F., 2018. Carbonic anhydrase, coral calcification and a new model of stable isotope vital effects. Geochimica et Cosmochimica Acta, 236, pp.179-197.
3. Uchikawa, J., Chen, S., Eiler, J.M., Adkins, J.F. and Zeebe, R.E., 2021. Trajectory and timescale of oxygen and clumped isotope equilibration in the dissolved carbonate system under normal and enzymatically-catalyzed conditions at 25° C. Geochimica et Cosmochimica Acta, 314, pp.313-333.

Requirements

In order to run the scripts you will need Matlab. The codes were produced using Matlab2017b but earlier and later versions will probably work just as well.

Scripts

1. Ion_by_ion_D61_D62_D63_D64_D65.m - A model for kinetic isotope effects in the CaCO₃-DIC system

This script provides an update to the ion-by-ion model of Watkins and Hunt (2015) in that it now includes Δ₆₄ and Δ₆₅. The script Ion_by_ion_D61_D62_D63_D64_D65.m was used to produce Fig. 2 of the paper. To run, simply download the script along with the following data files:

• Romanek_to_5C.txt
• Baker_to_5C.txt
• Watkins_to_5C.txt
• Levitt_to_5C.txt

2. The combined COAD Box Model

The COAD box model allows one to calculate kinetic isotopes effects in the full CaCO₃-DIC-H₂O system. The script Run_COAD_Box_Model.m was used to produce Fig. 6 of the paper.

The following scripts are required:

• CaCO3_DIC.m - this is the ion-by-ion function script
• COAD_Box_Model.m - this is the main script that calls CaCO3_DIC.m at each timestep
• Run_COAD_Box_Model.m - this is used to run COAD_Box_Model.m and post-process the outputs
• Tang_5C.m - data from Tang et al. (2014)