Dear All,
I would like to add to the pressure vs depth discussion that we have
been puzzled for a while by the crazy range of PT paths of all kinds of
shapes from otherwise VERY similar metamorphic LPHT terains - especialy
in Antarctica and central Australia.
Many of those PT paths published in the literature are based on a mere
DIRECTION that the PT path left the metamorphic peak. That is: The PT
path is often based on only the crossing of a tri- or divariant field by
some 10 MPa or so - may be less. In the light of the fact that
significant modal shifts may occur over a very few MPa in some divariant
fields relevant for metapelites, plus the fact that many LPHT terrains
show dramatic strainrate and temperature fluctuations during
metamorphism, we have published in 1994 and 1995 several papers on the
possible influence of non-lithostatic stresses on metamorphic PT paths.
If you are interested, our opinion on the subject was summarised in:
Stuewe & Sandiford 1994 JMG, 12, 445-454 and: Stuwe & Sandiford, 1955,
PEPI, 88, 211-221.
Kurt Stuewe
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Univ. Doz. Dr. Kurt Stuewe
Institut fuer Geologie und Palaeontologie
Universitaet Graz, Heinrichstr 26.
A-8010 Graz
Austria
email: [log in to unmask]
Fax: 0043-316-380-9870
ph: 0043-316-380-5682
http://bgeolm20.kfunigraz.ac.at
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