Hi Brian,
Thanks for a very prompt and helpful reply. I will try as you suggested by putting one kinetic rate law at a time with carbonates going in the last. I have considered a flow through system, however I wanted to do a stagnant system as a preceding step to it. Indeed a flow system might be more realistic. As for O2(aq), I was expecting small amount of Hematite and the model didn't allow me to precipitate Hematite without O2 in the basis.
One more issue that I sometimes face in GWB (not in this particular simulation): When I try to pick up the entire system (after a reaction path), the software changes the minerals in the system on its own. For example, in one of my models I tried to react CO2(g) in a stagnant system for 50 yrs. Then I picked the entire system and tried to react a brine using the flush model to mimic a flow-through system. But my original primary minerals were swapped out of the basis and new minerals were replaced. Do you know a way to get around this?
Many thanks for great suggestions.
Regards,
Vivek