Numerical Modelling of Multi-Phase Multi-Component. Reactive Transport in the Earth’s interior

Author (s): Oliveira, B. ; Afonso, J. C.; Zlotnik S. and Díez, P.
Journal: Geophysical Journal International

Volume: 212, Issue 1
Pages: 345 – 388
Date: 2018

Abstract:
We present a conceptual and numerical approach to model processes in the Earth’s interior that involve multiple phases that simultaneously interact thermally, mechanically and chemically. The approach is truly multiphase in the sense that each dynamic phase is explicitly modelled with an individual set of mass, momentum, energy and chemical mass balance equations coupled via interfacial interaction terms. It is also truly multi-component in the sense that the compositions of the system and its constituent phases are expressed by a full set of fundamental chemical components (e.g. SiO2, Al2O3, MgO, etc) rather than proxies. These chemical components evolve, react with, and partition into different phases according to an internally-consistent thermodynamic model. We combine concepts from Ensemble Averaging and Classical Irreversible Thermodynamics to obtain sets of macroscopic balance equations that describe the evolution of systems governed by multi-phase multi-component reactive transport (MPMCRT). Equilibrium mineral assemblages, their compositions and physical properties, and closure relations for the balance equations are obtained via a “dynamic” Gibbs free-energy minimization procedure (i.e. minimizations are performed on-the-fly as needed by the simulation). Surface tension and surface energy contributions to the dynamics and energetics of the system are taken into account. We show how complex rheologies, i.e. visco-elasto-plastic, and/or different interfacial models can be incorporated into our MPMCRT ensemble-averaged formulation. The resulting model provides a reliable platform to study the dynamics and non-linear feedbacks of MPMCRT systems of different nature and scales, as well as to make realistic comparisons with both geophysical and geochemical data sets. Several numerical examples are presented to illustrate the benefits and limitations of the model.

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Bibtex:

@article{doi:10.1093/gji/ggx399,
author = {Oliveira, B.; Afonso, J.C.; Zlotnik, S. and Diez, P.},
title = {Numerical modelling of multiphase multicomponent reactive transport in the Earth’s interior},
journal = {Geophysical Journal International},
volume = {212},
number = {1},
pages = {345-388},
year = {2018},
doi = {10.1093/gji/ggx399},
URL = { + http://dx.doi.org/10.1093/gji/ggx399},
eprint = {/oup/backfile/content_public/journal/gji/212/1/10.1093_gji_ggx399/1/ggx399.pdf}
}