Simulating calcite precipitation driven by silicate weathering

[poong9]

Hello everyone!

I'm trying to use Phreeqc to simulate that carbonate (calcite) precipitation can be the result of gypsum dissolution or silicate weathering.

I tried with the following input file for the case of gypsum dissolution:

SOLUTION 1
    temp      25
    pH        7
    pe        4
    redox     pe
    units     mmol/kgw
    density   1
    -water    1 # kg

END

USE solution 1
EQUILIBRIUM_PHASES 1
        Calcite   0 10
SAVE solution 2
END

USE solution 2
REACTION 1
    Gypsum     1
    1 millimoles in 1 steps
EQUILIBRIUM_PHASES 2
    Calcite   0 0 precipitate_only
   Save solution 3
END

And the results clearly showed that some calcite precipitated.
But I failed when it comes to silicate weathering (I used Anorthite and/or Albite for my model).

Could anybody take a look and help me with this problem?

Thank you very much!!!

[dlparkhurst]

Here is a simple soil-zone weathering calculation.

Code: [Select]

SOLUTION 1
    temp      25
    pH        7
    pe        4
    redox     pe
    units     mmol/kgw
    density   1
    -water    1 # kg

END

USE solution 1
EQUILIBRIUM_PHASES 1
    Calcite   0 10
    CO2(g)    -2.5 10
SAVE solution 2
END

USE solution 2
REACTION 1
    Anorthite  1
    1 millimoles in 1 steps
EQUILIBRIUM_PHASES 2
    Calcite   0 0 precipitate_only
    Chalcedony 0 0
    Kaolinite 0 0
    CO2(g)    -2.5 0
SAVE solution 3
END

[poong9]

Thank you very much Dr. Parkhurst.