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Help with React Input - Flush model


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I am a GWB newbie, and I'm trying to model chemical changes in a basaltic rock when I run water through it at elevated temperatures and CO2(g) fugacities. I am trying to use the flush model, and possibly also a kinetic reaction path (I'm trying to plot changes over time, e.g. 1000 yrs, if I control the rate at which water is moving through the rock, e.g. 1 kg of water/year moving through ~ 1 kg of rock).


I am repeatedly getting one of 2 error messages:


either "Residual's too large, 621th interation" if I have something set for the charge balance (I have tried Cl-, Na+, both with a set value, based on N-MORB concentrations, or with no value put in - the only thing that changes is which iteration I get stuck on).


or "N-R didn't converge after 999 its., maximum residual = 1.#R, Xi = 0.0000" if I turn off the charge balance completely.


How can I fix my charge balance? Or, even, is my entire approach wrong?


I'm attaching the script of the code I'm using for this model.


Thank you for any help or advice!



Emily P.

EmilyP - GWB Script for Exp 1v3.txt

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Thank you for any help or advice!


Hi Emily:


Two points that will hopefully move you in the right direction:


  1. It looks like you've put rock mass and not fluid concentration data into the Basis pane. GWB requires that you put an aqueous system of some kind into the Basis pane. One option would be to constrain the concentrations of fluid components initially in equilibrium with your basalt, and then flush water through as a reactant. Your other option would be to titrate the minerals or oxides composing your basalt in as Reactants into your Basis fluid (a reverse titration model).
  2. Specifying a beginning and end time does not make a model kinetic, it simply creates an equilibrium model in which the reaction path variable is time. To create a kinetic model, you'll want to add a kinetic mineral in the Reactants pane - have a look at the GWB Reaction Modeling Guide, which has a large section on kinetics.


I hope that helps,


Tom Meuzelaar

RockWare, Inc.

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