Colleagues

We invite you to participate in the following session at the EGU - AGU -
EUG Joint Assembly, Nice, France, April 2003 (see
http://www.copernicus.org/egsagueug/index.html ). Abstract deadline is
January 15, very early registration deadline is December 31 (save Euro 60),
early registration deadline is March 7 (save Euro 30).

TS2.05 Heat and mass transfer from depth: Metamorphism and Crustal Melting
in Orogenesis - from Microstructures to Tectonics

A correlation between extent of melting during high P-high T granulite
metamorphism and orogenic evolution has been postulated that may be
controlled by crustal composition. For example, metapelitic rocks increase
the radiogenic heat budget and the low solidus temperature of metapelites
allows extensive melting. As a result, orogens containing significant
amounts of metapelite are more susceptible to widespread, melt-induced
weakening than orogens dominated by either quartzo-feldspathic or mafic
compositions or older melt-depleted crust. Thus, mechanisms of granulite
terrain exhumation may also be a function of extent of melting and
therefore of composition. Observations of granulite terrains worldwide
support this conclusion. For example, many ultrahigh-temperature granulite
terrains exhibit a characteristic mylonitic fabric formed during exhumation
that generally hinders recognition of the earlier history, and
retrogression to 'common' granulite may obscure both the extent of melting
and the extreme nature of the thermal anomaly associated with the
metamorphism (eg., Bohemian Massif, Brazilia Fold Belt). This contrasts
with granulites in Fiordland, New Zealand, where vertical planar reaction
zones occur in gabbro due to melting in adjacent metadiorite and melt
escape through fractures in the gabbro where melt scavenged water to induce
limited recrystallization to garnet granulite. The mechanisms of formation
and exhumation of high-grade rocks of different bulk compositions in
different orogens and the source of heat in UHT metamorphism are
fundamental questions in generating and exhuming high-grade terrains that
will be addressed by this symposium. We anticipate that the symposium will
attract interest across the spectrum from petrology to tectonics and from
microstructures to geophysics, and that it will include contributions from
field-based research, experiments and modeling.

Convenors:
Mike Brown (University of Maryland, E-mail: [log in to unmask])
Paddy O' Brien (Universitaet Potsdam, E-mail: [log in to unmask])
Tracy Rushmer (University of Vermont, E-mail: [log in to unmask])


***************************************************************************
Michael Brown
Professor of Geology
and Chair of Department

Department of Geology           [log in to unmask]
Geology Building                        http: www.geol.umd.edu
University of Maryland          Direct line: 301 405 4080
College Park                            Exec. asst.: 301 405 4065
MD 20742-4211                   Dept. office: 301 405 4082
USA                                     Direct fax: 301 314 7970
                                        Dept. fax: 301 314
9661

***************************************************************************
LABORATORY FOR CRUSTAL PETROLOGY (Information at:
http: www.geol.umd.edu/pages/faculty/BROWN/lcp.htm)
***************************************************************************