Dear Scott and others,
These are interesting and important questions. Apart from sgnificant
differences in computational strategies, the Domino and Perplex database
formats may not allow you to make identical thermodynamic
implementations of solid solution models (especially if you use the van
Laar formalism for amphiboles).
There are several models for amphiboles (Dale et al. 2000, 2005, Okamoto
& Toriumi 2004, Mäder & Berman), which one do you think is the best?
I don't want to discourage you, but I choose either software based on
the problem at hand. If reciprocal solutions are involved (in your
case, biotite and amphibole), I perform a few simple minimizations and
look if assemblage and phase compositions for a given bulk, P and T
come out from Domino/Theriak and Perplex comparably. If you get
different results, this is still no surprise at this stage.
Theriak may run into serious problems with reciprocal solutions,
especially when reciprocal Gibbs free energies are zero (implicit in the
Holland-Powell ideal models), only sometimes you may get negative mole
fractions still leading to realistic site fractions. I don't think that
you can incorporate van Laar size parameters of the latest amphibole
model in Theriak/Domino. My preference would be Perplex, but make sure
that you cover adequate composition space (check for edenite and
ferroedenite, if these are accessible in Perplex, if relevant for your
problem).
David
Scott Johnston wrote:
> Hello - I have been using Domino and Perple_X to make pseudosections, and I
> have a couple of questions with regard to Domino:
>
> 1) In domino, is there any way to make isopleths for Mg content in biotite?
> I have successfully made isopleths for phlogopite, however, these isopleths
> exclude a lot of Mg that goes into the obiotite solution for biotite, and
> thus yields isopleths that are less than the true Mg content. Is there any
> way to get around this and create isopleths that reflect the total Mg content?
>
> 2) Perple_X has several solution models for amphibole; I have been using
> GlTrTsPg. In Domino, I have been using the database tcdb55c2.txt which does
> not have any amphibole solution models. Is there a database for Domino that
> I could use that incorporates a solution model for amphibole similar to
> GlTrTsPg?
>
> Thanks, Scott Johnston
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David Dolejs (postdoc/geochemistry)
Bayerisches Geoinstitut
University of Bayreuth
D-95440 Bayreuth Tel: +49 921 553717
Germany Fax: +49 921 553769
http://www.users.bgi.uni-bayreuth.de/~d_dolejs/
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