Hi Dmitry (and fellow ternary feldspar activity tweakers)l
there is an error in the table of mixing parameters in the published
Fuhrmann and Lindsley paper. The values for OrAn and AnOr are in the wrong
order. This has never been officially corrected but most people using the
model have realised the error. The programs from Lindsley and from Nekvasil
use the correct values. The distributed version of the TWQ database uses
the published (i.e. incorrect) values but in addition uses a different
ternary interaction formulation that results in calculation of
significantly different component activities for K-feldspar in HT ternary
At 03:51 28.11.2001 +0300, you wrote:
>Thank you very much for 2Fsp thermometric programs and refs to websites:
>with your help, I've got 'em all!
>But, I have another question regarding these programs - and, especially,
>ternary feldspar model of Fuhrman & Lindsley, 1988 (AM'88, NN3-4,
>pp.201-215). I've been surprised that I cannot reproduce T's calculated by
>2Fsp programs (with F&L'88 model and even fixed mineral compositions).
>Comparison of W-parameters revealed that enthalpy terms (WH) for An-Or join
>are in opposite places in the paper and SOLVCALC database (i.e. WH[AnOr]
>and WH[OrAn] are swapped somewhere). So, the question is: where is a typo -
>in the paper, or in all the programs I have got now? T's presented in the
>same paper suggested me, that typo is in its table with Margules
>This may be interesting for those who use TWQ program: its databases use
>F&L'88 model with parameters taken directly from that table;) Otherwise,
>what's about MTHERM3 and SOLVCALC?
>To say, such swapping lead to 74(!)deg. differences in calculated
>"anorthitic" temperatures for the trachyte sample from Carmichael (1965)
>(1st sample from Table 3, F&L'88, calced with fixed compositions).
>Dmitry V. Dolivo-Dobrovolsky
>Institute of Precambrian Geology and Phone: +7(812)273-02-79 home
>Geochronology, the Russian Academy +7(812)328-03-62 work
>of Sciences Fax: +7(812)328-48-01 work
>Makarova emb. 2
>199034 St.-Petersburg E-mail: [log in to unmask]