Setting Excess Phases

[Metamorphi]

Hello Nicolas,

Firstly, congratulations on this excellent program, it is simply easy to use and the new Julia web interface just adds to that. I am very impressed.

Not so much a problem, as a clarification here:

I am modelling a sub-solidus metabasite using the Green et al (2016) solution models, and I have set the bulk H2O content to '0', setting it in excess. I want to clarify if setting the H2O to 0 is MAGEMin's equivalent of excess, or is there some other way I may have overlooked (I haven't used the Matlab interface)?

Setting H2O to 0 in the bulk generates some higher P fields (10 - 12 kbar) containing two feldspars (ksp & ksp) indicating an extremely dry rock, and in some cases saturating the bulk (in a T-XH2O section) gives some fields with 2 hb phases.

Thanks again!

[NicolasRiel]

Hi,
Thanks for the support!
You are raising a very good point. This is something I was discussing with the TC team not so long ago because I wanted to a add reduced chemical system without water for the metabasite dataset.
But actually, the metabasite database has not been developed for dry cases (as far as I understand), therefore they told me it did not make sense to have a water content = 0.0.
The results you get by explicitly setting water to 0.0 are likely bogus. For the "dry(ish)" case I suggest you just prescribe a low water content such as 0.01 mol% of H2O.
If you need excess water just provide a large amount of water. Presently, I don't have a clean "excess" mode, but I will add that eventually. By clean, I mean that by setting a large value of H2O, H2O will always appear in the output with variable content, although it should only be stated that water is in excess.

There is a number of things that need to be better explained. I will expand the documentation as soon as possible.

Hope this helps,

Nicolas