Eric, thank for your response, but it cause new questions.
1-Jun-99 14:21 Eric Essene wrote:
> Pavel,
> In their book on kinetics, Wood and Walther estimated the overstepping
> of metamorphic dehydration reactions to be only 5°C or so at moderate T.
It seems that I don't know this book. How is it titled? However, I
saw similar estimations in their papers. I not quite understand
how they were made. By the way, in their paper (Contr.Min.Pet.
v88, 1984) Walther and Wood considered overstepping in the
interval 0-100C.
> However, Austrheim has shown that 1.0 Ga garnet granulites only transformed
> to 0.45 Ga eclogites on Holsnøy Is., Norway, where mylonites and even
> pseudotachylytes are found, or when hydrous veins cut the granulites. The
> implication is that dry granulites survived a metamorphic event at 18-20
> kbar and 650-700°C without fully transforming.
In this case reason for inhibition of reactions is absence of
reaction agent (water or, more exactly, salted fluid). The problem
of overstepping (supersaturation) during reaction seems to be more
interest for me. What is driving force of metamorphic reactions?
Many metamorphic textures, especially in metasomatites, point us
to sufficient disequilibrium (though interpretation of textures is
really like to art, we have some basements, including
cristallographic investigations, for it).
Pavel.
--
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Pavel Azimov
Institute of Precambrian Geology and Geochronology
Russian Academy of Sciences
2, Makarov Embankment
St.Petersburg, 199034, Russia
Phone: +7(812)328-03-62
Fax: +7(812)328-48-01
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