At 11:37 AM 27/03/2003 -0500, Jorge Julian Restrepo wrote:
>...
>The assemblages are:
>chlorite-tremolite
>tremolite-antophyllite
>actinolite-talc-chlorite
>antigorite-tremolite-antophyllite-chlorite-relict olivine
According to either the Berman1988 or the HollandPowell1998 thermochemical
database (and taking account of Mg-Fe2+ partitioning based on analyses of
coexisting minerals in metaperidotite by Evans and Trommsdorff),
antigorite+anthophyllite+V is everywhere less stable than olivine+talc+V.
Hence the last assemblage is problematic whether or not the olivine is
"relict".
Either tremolite+anthophyllite+chlorite+olivine(+retrograde antigorite),
or antigorite+tremolite+chlorite+olivine(+relict anthophyllite)
would be compatible with experimental phase equilibria. The first
assemblage has an upper limit of P at ~13 kbar, 630 degC and an upper limit
of T at ~6 kbar, 740 degC.
Dugald M Carmichael Phone/V-mail: 613-533-6182
Dept of Geological Sciences and Geological Engineering
Queen's University FAX: 613-533-6592
Kingston ON K7L3N6 E-mail: [log in to unmask]
|