A Tractable Approach to Coupling the Thermodynamics, Kinetics, and Fluid Dynamics of Mantle Melting
Abstract
The composition of new igneous crust is thought to be strongly modulated by the dynamics of melt transport in the convecting mantle. Understanding the various feedbacks between reaction and melt transport requires consistent coupling of multicomponent multiphase thermodynamics and geodynamics. However, the high-dimensionality of such coupled problems poses a major challenge.
Here we present a new theoretical and software framework for integrating general multiphase thermodynamics into magma dynamics simulations. Our approach is based on the theory of non-equilibrium thermodynamics in which reaction is treated as an irreversible process, and extends existing magma dynamics theories in a number of ways. Firstly, we extend the conservation equations for two-phase flow to allow for multiple solid phases, and more general solid rheologies. Interphase mass transfer is then formulated in terms of a set of stoichiometric reactions. The rates of these reactions are controlled by their respective chemical affinities and may be turned on or off when reactants are exhausted. A key factor facilitating this approach is the development of flexible thermodynamic modeling software as part of the ENKI project, that allows reproducible development of custom thermodynamic and kinetic libraries that can be incorporated into dynamic models (and other software). We apply this framework to model poro-viscous behavior in the Mg2SiO4-SiO2 binary system, which is used as an analogue for eutectic/peritectic-style mantle melting. We simulate processes including the melting and reaction of a fusible eclogite (qz + opx) heterogeneity within a harzburgitic mantle (ol + opx), and reactive transport in a harzburgitic mantle column.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.V21B..02T
- Keywords:
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- 1011 Thermodynamics;
- GEOCHEMISTRY;
- 1042 Mineral and crystal chemistry;
- GEOCHEMISTRY;
- 8124 Earth's interior: composition and state;
- TECTONOPHYSICS;
- 8178 Tectonics and magmatism;
- TECTONOPHYSICS