Not formally, no. At low T for many pelite/psammitic compositions, going up temperature you do predict the sequence pure ab at low T, a small pure ab field coexisting with albitiic plagioclase, followed by plagioclase solid solution at higher T.  The HP 2003 plagioclase solution model by itself does not predict a peristerite gap. 

Doug

On 2018-05-07, 2:45 PM, "Dugald Carmichael" <[log in to unmask]> wrote:

    May I ask does the "MTlow" solution-model take adequate account of the field-postulated "peristerite-solvus" between albite and oligoclase in metamorphic plagioclase?
    
    Dugald
    
    -----Original Message-----
    From: Metamorphic Studies Group [mailto:[log in to unmask]] On Behalf Of Doug Tinkham
    Sent: May 7, 2018 1:35 PM
    To: [log in to unmask]
    Subject: Re: Phase diagrams with THERIAK-DOMINO
    
    Hi Gisela
    
    You might also try a slightly older version of Theriak-Domino from my website (if you are using Windows) from http://dtinkham.net/peq.html. I haven't had time to put up the mac binaries yet. That version does a slightly better job for some of the problematic mode zero boundaries. See attached. The 2017 version sometimes has more of a problem, and all of those horizontal lines trying to connect different boundaries is a sign of the problem. 
    
    You will rarely remove all of the squiggles or incomplete lines when working in a 9-11 component system over a large P-T range like this. A good approach is to use both Theriak-Domino (TD) and thermocalc in combination, using TD to get the majority of the fields determined, and then use thermocalc to construct the final diagram. In fact, you could just use Theriak to calculate the equilibrium assemblages at individual P-T points, and then use thermocalc to calculate the diagram with just limited knowledge of the equilibrium assemblage and phase compositions at a few points. Manual construction in thermocalc is an excellent way to learn phase equilibria even though it is more time consuming.
    
    Finally, if you are going to calculate down to low temperatures like you are, you should activate the ab pure end-member, which might have inadvertently been deactivated in that file.
    
    
    Doug
    
    
    
    On 2018-05-07, 8:06 AM, "Metamorphic Studies Group on behalf of Erik Duesterhoeft" <[log in to unmask] on behalf of [log in to unmask]> wrote:
    
        Hi Gisela,
        
        you are using the wrong solution model. MTlow should be used at 
        greenschist up to amphibolite grade. If you are looking at suprasolidus 
        conditions use the MThi model. I hope this will solve your problem.
        
        Cheers,
        
        Erik
        
        -- 
        Erik Duesterhoeft
        Institute of Geosciences,
        University of Kiel
        Ludewig-Meyn-Str. 10
        D-24118 Kiel
        Room 454
        
        
        Am 5/7/18 um 11:50 AM schrieb Gisela Leoz Munte:
        > Dear colleagues,
        >
        > I'm having some trouble with the generation of some phase diagrams 
        > with the program THERIAK-DOMINO. I'm trying to plot the composition of 
        > a High-K mica rich metapelitic schist and of a qz rich semipelitic 
        > gneiss in aims to constrain their P-T metamorphic conditions. After 
        > calculating the local bulk composition of my samples, the outputed 
        > diagrams show some  problematic areas with some strange instabilities 
        > (see those lines interrupting the diagram; see attached images) of 
        > wich I cannot establish its origin, as I find myself unable to locate 
        > the problem that causes them.
        >
        > Has anyone encountered this before? If so, anyone knows how can I fix 
        > the problem? I'm using the td-tcds62-6axmn-03.txt  database, and I've 
        > been able to plot the T-X diagram with it, but not the P-T diagrams.
        >
        >
        > Thanks in advance! Any help would be highly appreciated
        >
        >
        > Gisela Leoz
        >
        >