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) ***************************************************************************