Coupling between Thermo-Hydro-Chemical reactive transport and Gibbs minimisation: magma evolution in evolving multiphase porous media

2020 ◽  
Author(s):  
Annelore Bessat ◽  
Sébastien Pilet ◽  
Stefan M. Schmalholz ◽  
Yuri Podladchikov
Keyword(s):  
Gibbs Energy ◽  
Reactive Transport ◽  
Viscous Medium ◽  
Physical Aspect ◽  
Magma Evolution ◽  
Energy Minimisation ◽  
Transport Code ◽  
Low Degree ◽  
Melt Percolation ◽  
Alkaline Magmas

<p>The formation of alkaline magmas observed worldwide requires that low degree-melts, potentially formed in the asthenosphere, were able to cross the overlying lithosphere. Fracturing in the upper, brittle part of the lithosphere may help to extract this melt to the surface. However, the mechanism of extraction in the lower, ductile part of the lithosphere is still contentious. Metasomatic enrichment of the lithospheric mantle demonstrates that such low-degree melts interact with the lithosphere, but the physical aspect of this process remains unclear. The aim of this study is to better understand the percolation of magma in a porous viscous medium at pressure (P) and temperature (T) conditions relevant for the base of the lithosphere. We study such melt percolation numerically with a Thermo-Hydro-Chemical model of reactive transport coupled with thermodynamic data obtained via Gibbs energy minimisation. We perform Gibbs energy minimisation with Matlab using the linprog algorithm. We start with a simple ternary system of Forsterite/Fayalite/Enstatite solids and melts. All variables are a function of T, P and composition of the system (C), and are computed in both the Gibbs energy minimisation and in the reactive transport code, and can therefore vary freely.</p>

Melt migration by reactive porosity waves

2021 ◽  
Author(s):  
Annelore Bessat ◽  
Sébastien Pilet ◽  
Stefan M. Schmalholz ◽  
Yuri Podladchikov
Keyword(s):  
Gibbs Energy ◽  
Numerical Algorithms ◽  
Wave Model ◽  
Physical Aspect ◽  
Melt Migration ◽  
Energy Minimisation ◽  
Porosity Wave ◽  
Low Degree ◽  
Silica Concentration ◽  
The Impact

<p>The formation of alkaline magmas observed worldwide requires that low degree-melts, potentially formed in the asthenosphere, were able to cross the overlying lithosphere. Fracturing in the upper, brittle part of the lithosphere may help to extract this melt to the surface. However, the mechanism of extraction in the lower, ductile part of the lithosphere is still contentious. Metasomatic enrichment of the lithospheric mantle demonstrates that such low-degree melts interact with the lithosphere, but the physical aspect of this process remains unclear.</p><p>Here, we aim to better understand, first, the percolation of magma in a porous viscous medium at pressure (P) and temperature (T) conditions relevant for the base of the lithosphere, and second, the impact of chemical differentiation on melt migration. We investigate theoretically the process of melt migration employing the fundamental laws of physics and thermodynamics. We simulate melt percolation numerically with a one-dimensional (1-D) Thermo-Hydro-Mechanical-Chemical (THMC) model of porosity waves coupled with thermodynamic results obtained from numerical Gibbs energy minimisation calculations. We perform THMC modelling and Gibbs energy minimisations with self-developed numerical algorithms using MATLAB and linear programming routines. We employ a simple ternary system of Forsterite/Fayalite/Enstatite for the solid and melt. Model variables, such as solid and melt densities or mass concentrations of MgO and SiO in solid and melt, are a function of pressure (P), temperature (T) and total silica concentration of the system (X). These variables are pre-computed with Gibbs energy minimisation and implemented in the THMC porosity wave transport code via parameterized equations, determining the T-P-X dependence of the model variables.</p><p>First results show that the total silica concentration and the temperature gradient are important parameters to consider in melt migration by reactive porosity waves. We discuss results of a systematic series of 1-D simulations and we present preliminary results form a 2-D reactive porosity wave model.</p>

scholarly journals Feldspar megacrysts and anorthosite xenolith-bearing dykes in the Narssarssuaq area, South Greenland

1992 ◽  
Vol 154 ◽  
pp. 49-59
Author(s):  
T Winther
Keyword(s):  
Open Systems ◽  
Early Stage ◽  
Rift System ◽  
Magma Chambers ◽  
Degree Of Contamination ◽  
Magma Reservoirs ◽  
Incompatible Elements ◽  
Low Degree ◽  
Alkaline Magmas ◽  
Compositional Gradients

Numerous dyke intrusions are found in the Narssarssuaq area of the Gardar province, a Mid-Proterozoic intracontinental rift system. Ten to fifteen percent of these dykes, which range in composition from trachybasalt to phonolite and rhyolite, contain significant proportions of feldspar megacrysts and occasionally anorthosite xenoliths. Two groups of dykes are distinguished; the older group is more alkaline, richer in incompatible elements and contains more anorthosite xenoliths than the younger. It is probable that the main reason for the differences is variation in magma production through time and from one area to another. Chemical zonation in the dykes reflects compositional gradients in the feeding magma reservoirs; the magma reservoirs acting as open systems in which crystal fractionation was an important controlling process. The anorthosite xenoliths are not strictly cognate with their hosts, but were derived from comparable alkaline magmas with a composition roughly corresponding to the most primitive of the dykes. The plagioclase megacrysts were presumably formed at an early stage of the development of the magma chambers. Rb-Sr dating of one of the dykes from the older group of dykes gives an age of 1206 ± 20 Ma and an initial 87Sr/86Sr ratio of 0.7028 ± 0.0001 supporting a low degree of contamination with upper crustal Sr.

scholarly journals Predicting Fluid Properties in the MUFITS Reservoir Simulator with User-Supplied Modules

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Andrey Afanasyev ◽  
Ivan Utkin
Keyword(s):  
Phase Equilibria ◽  
Reactive Transport ◽  
Source Code ◽  
Considerable Effort ◽  
Property Prediction ◽  
Energy Minimisation ◽  
Fluid Properties ◽  
Reservoir Simulator ◽  
Software Extension ◽  
Fluid Parameters

We present a recent development of the MUFITS reservoir simulator aiming at modelling the transport of fluids whose properties and phase equilibria are calculated in a user-supplied external shared library. Both the explicit correlations and tabulated data for the fluid parameters can be implemented in the library that we name the EoS-module (Equation of State-module). An iterative approach—which, for example, is based on the phase equilibria calculation through the Gibbs energy minimisation (GEM) method, can also be used in the EoS-module. A considerable effort has been undertaken to minimise the number of program procedures exported by the shared library. This should facilitate and ease the usage of the developed software extension by the scientific community. Furthermore, we supplement the article with the source code of two simple EoS-modules that can serve as templates in other modelling and software development efforts. The EoS-modules are also useful for coupling MUFITS with other elaborate software for fluid property prediction. To demonstrate such a possibility, we supplement the article with the source code of a more complicated EoS-module that couples MUFITS with the geochemical code GEMS3K. This module is used in a simple 1-D benchmark study showing the capabilities of MUFITS for modelling reactive transport in porous media.

Presentation and use of a reactive transport code in porous media

2007 ◽  
Vol 32 (1-7) ◽  
pp. 507-517 ◽  
Author(s):  
Ph. Montarnal ◽  
C. Mügler ◽  
J. Colin ◽  
M. Descostes ◽  
A. Dimier ◽  
...  
Keyword(s):  
Porous Media ◽  
Reactive Transport ◽  
Transport Code

scholarly journals Sorption modelling by Gibbs energy minimisation: Towards a uniform thermodynamic database for surface complexes of radionuclides

2002 ◽  
Vol 90 (9-11) ◽  
Author(s):  
D. A. Kulik
Keyword(s):  
Solid Solution ◽  
Aqueous Solution ◽  
Gibbs Energy ◽  
Mineral Water ◽  
Reference Site ◽  
Surface Complexes ◽  
Common Value ◽  
Energy Minimisation ◽  
Site Density ◽  
Elemental Stoichiometry

SummaryRadionuclide sorption on mineral-water interfaces can be thermodynamically modelled, similar to solid-solution aqueous-solution systems (only in chemical elemental stoichiometry), if definitions of the standard and reference states, surface activity terms (SAT), and elemental stoichiometries of surface-bound species are unequivocally established. A pre-requisite is that a unique common value of the reference (site) density (Γ

scholarly journals Addressing numerical challenges in introducing a reactive transport code into a land surface model: a biogeochemical modeling proof-of-concept with CLM–PFLOTRAN 1.0

2016 ◽  
Vol 9 (3) ◽  
pp. 927-946 ◽  
Author(s):  
Guoping Tang ◽  
Fengming Yuan ◽  
Gautam Bisht ◽  
Glenn E. Hammond ◽  
Peter C. Lichtner ◽  
...  
Keyword(s):  
Land Surface ◽  
Reactive Transport ◽  
Computing Time ◽  
Reaction Network ◽  
Transformation Method ◽  
Residual Concentration ◽  
Log Transformation ◽  
Time Stepping ◽  
Transport Code ◽  
Scaling Methods

Abstract. We explore coupling to a configurable subsurface reactive transport code as a flexible and extensible approach to biogeochemistry in land surface models. A reaction network with the Community Land Model carbon–nitrogen (CLM-CN) decomposition, nitrification, denitrification, and plant uptake is used as an example. We implement the reactions in the open-source PFLOTRAN (massively parallel subsurface flow and reactive transport) code and couple it with the CLM. To make the rate formulae designed for use in explicit time stepping in CLMs compatible with the implicit time stepping used in PFLOTRAN, the Monod substrate rate-limiting function with a residual concentration is used to represent the limitation of nitrogen availability on plant uptake and immobilization. We demonstrate that CLM–PFLOTRAN predictions (without invoking PFLOTRAN transport) are consistent with CLM4.5 for Arctic, temperate, and tropical sites.Switching from explicit to implicit method increases rigor but introduces numerical challenges. Care needs to be taken to use scaling, clipping, or log transformation to avoid negative concentrations during the Newton iterations. With a tight relative update tolerance (STOL) to avoid false convergence, an accurate solution can be achieved with about 50 % more computing time than CLM in point mode site simulations using either the scaling or clipping methods. The log transformation method takes 60–100 % more computing time than CLM. The computing time increases slightly for clipping and scaling; it increases substantially for log transformation for half saturation decrease from 10−3 to 10−9 mol m−3, which normally results in decreasing nitrogen concentrations. The frequent occurrence of very low concentrations (e.g. below nanomolar) can increase the computing time for clipping or scaling by about 20 %, double for log transformation. Overall, the log transformation method is accurate and robust, and the clipping and scaling methods are efficient. When the reaction network is highly nonlinear or the half saturation or residual concentration is very low, the allowable time-step cuts may need to be increased for robustness for the log transformation method, or STOL may need to be tightened for the clipping and scaling methods to avoid false convergence.As some biogeochemical processes (e.g., methane and nitrous oxide reactions) involve very low half saturation and thresholds, this work provides insights for addressing nonphysical negativity issues and facilitates the representation of a mechanistic biogeochemical description in Earth system models to reduce climate prediction uncertainty.

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