Dear Dazhi,
as I remember, it is only "allowed" and reasonable to apply PT calculations
when there is evidence of a textural and/or chemical equilibrium. In
high-strain zones this is hardly realized. if it is evident that
recrystallisation took place and a textural/structural equilibrium is
manifested, at least in part of, the mineral-chemistry and texture, then
there is no reason to assume higher pressures than suggested by the
Barometer. The concept of "tectonic-overpressure" is discussed in some
papers (e.g. Mancktelow 93; SMPM, 73, 340-341 and Carswell 90; in Carswell
90 ed. Eclogites and eclogite facies rocks, pp.1-13, Blackie, Glasgow)
Best Regards
Robert
>Dear all:
>
>Geologists now commonly use geothermobarometry to estimate
>the P-T condition of tectonometamorphic events. When
>interpreting the tectonic history of an area, we routinely convert the
>estimated pressure to depth assuming that the pressure was
>lithostatic and due completely to the load of overlying rocks. In
>high-strain zones this assumption cannot be justified.
>
>Dose anyone know any other ways of estimating the depth of a
>tectonometamorphic event? Please advise me to the relevant
>references. Thanks.
>
>
>Sincerely,
>
>********************************************************************
>Dazhi Jiang, Assistant Professor
>Department of Geology
>University of Maryland
>College Park, MD 20742
>Phone:(301) 405-6979, Fax:(301)314-9661
>e-mail: [log in to unmask], http://www.geol.umd.edu
>*************************
------------------------------------------------------------------
Robert Schmid
Institut für Geowissenschaften der Universität Potsdam
Postfach 601553
D-14415 Potsdam
GERMANY
Tel. +49/331/977-2910
Fax +49/331/977-2087
[log in to unmask]
http://www.uni-potsdam.de/u/Geowissenschaft/index.htm
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