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Complex solid solutions and constrained minimum

Posted: 05 Nov 2015, 10:49
by Erik Duesterhoeft
What bothers me often is the question, how well are the complex (reciprocal) solution models defined. For example, let’s consider the complex solid solution model of amphiboles from Diener et al., 2012. I often calculate stability fields with two, three or even four co-existing amphibole phases from the same solution. I have the feeling that this cannot be true and it is an artificial effect from the formulation of the a-x model. In my opinion these fields are better presented by a single solid solution phase. And here is my question:

Am I allowed to generate a constrained minimum by not allowing two or more co-existing phases from the same solution?
(This can be done by changing the EQUALX parameter in the theriak.ini file to 1E+2; as long as no other phases are effected, e.g. two co-existing feldspars)

However, it’s just an idea that came up. What’s your opinion?