47-8 MinKin: A Computational Tool for Modeling the Kinetics of Multi-Component Geochemical Systems

Session: Minerals in Motion: Tracking Mineral Reactions Using In Situ and Synchrotron Techniques, A Celebration of the Career of Peter Heaney

Presenting Author:

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Abstract:

Understanding the kinetics of geochemical reactions often involves fitting rate laws to a time-series of experimental concentration data in order to extract rate constants for individual reactions. However, natural systems of interest often involve multiple mineral phases reacting with components of a fluid phase, making it intractably complex to solve the system's differential equations (i.e., rate equations) in order to fit them to experimental concentration data. In this contribution we describe MinKin (for “Mineral Kinetics”), a global optimization code for Matlab capable of fitting a standard chemical kinetic model to experimental concentration data even in the absence of closed-form solutions to the system's kinetic equations.¹ MinKin allows users to specify the species and reactions of a geochemical system consisting of a fluid with many aqueous species and up to three mineral species, and then uses the global optimization algorithm of Differential Evolution (DE)^2,3 to calculate the rate constants that minimize the error between the model and the data. Trial calculations reveal that MinKin is able to simultaneously and correctly calculate up to six rate constants on a time scale of minutes (and up to ten rate constants on a time scale of hours) with a relative error roughly the same magnitude as that of the input data. This makes MinKin a powerful way to analyze the kinetics of multi-component geochemical systems -- especially for important natural systems such as those studied during Peter Heaney’s long and influential career, in which isolating individual reactions is often infeasible but mineral transformations can still be measured in situ.

[1] D.R. Hummer, P.J. Heaney. (2015) Chemical Geology 405, 112-122.

[2] R. Storn, K. Price. (1997) J. Global Optimization 11, 341-359.

[3] K. Price, R. Storn. (1997) Dr. Dobbs Journal  22(4), 18-24.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10268

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