Limit of saturation index of minerals in REACT?

[thais98]

Happy new year everybody

So, apparently there's a limitation of the saturation index of the minerals when using the REACT, it doesn't get supersaturated. No matter how much of a mineral I add to the reactants, I always get the same saturation index for calcite. I would like to know if there's a way that I can change that, in order to get a higher S.I for the minerals. In the file I attached, the CO2 that was left in solution is 3.444e-06 , and that's the maximum it's consumed when reacting with the other minerals. 

Thank you ^^

amostra 8- reagindo com rocha3.rea

[Jia Wang]

Hello Thais98,

As far as I can tell, there doesn't seem to be a limit to the degree of supersaturation. I ran your React file and saw that calcite did become supersaturated with respect to the fluid at an early point in your simulation. If you copy and paste the mineral saturation data to an excel spreadsheet, you can see that Q/K is greater than 1 at some early points of the simulation, which indicates that calcite is supersaturated with respect to the fluid. When that occurs, calcite is precipitated at a rate prescribed by the rate law. You can check this by looking at the dissolution rate and mineral volume precipitated in Gtplot . Calcite is initially undersaturated and thus has a negative dissolution rate, which indicates that it is precipitating. The time at which the fluid becomes supersaturated is when the calcite starts precipitating. Then the calcite reaches equilibrium with the fluid and other more stable minerals started precipitating out, like Prehnite, Gibbsite, etc. If you would like to see an example of a supersaturated fluid, you might be interested in the fluid mixing unit on the GWB Academy. 

 

Hope this helps,

Jia Wang

[thais98]

Hello, Thank you very much for your answer.

I saw it again and you are right!