Aluminosilicates with Impurities

[stewa184]

I have been attempting to perform inverse modeling of water interacting with aluminosilicates. Starting from precipitation I would like to see the reactions that result in the observed streamwater. I have done XRD analysis on the rock matrix to determine what minerals are present. Some of the minerals like Hedenbergite (CaFeSi2O6) seem like strong possible candidates to use in inverse modeling. However, whenever I use any elements that aren't major ions (Fe, Mn, ect.) PHREEQC does not seem to use them in inverse modeling.

Aluminosilicates involve dissolution of Al+3 and seem to work fine without known concentrations of Aluminium. Is there a way to have metals such as Fe and Mn behave the same?

[dlparkhurst]

If you add an Fe-containing mineral in INVERSE_MODELING; -phases, the a mole balance equation for Fe is automatically added. If Fe is included in the SOLUTION definitions, then those concentrations are considered, otherwise they are assumed to be zero. Concentrations of Fe are generally small, so the mole balance will essentially conserve iron among the phases. So you will have sources and sinks of iron such that net accumulation in solution is small.