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High-pressure/low-temperature metamorphism of basalts in Lavrion (Greece); implications for the preservation of peak metamorphic assemblages in blueschists and greenschists

Ioannis Baziotis, Alexander Proyer and Evripidis Mposkos
High-pressure/low-temperature metamorphism of basalts in Lavrion (Greece); implications for the preservation of peak metamorphic assemblages in blueschists and greenschists
European Journal of Mineralogy (January 2009) 21 (1): 133-148

Abstract

The Upper Tectonic Unit of the Lavrion area is part of the Attic-Cycladic blueschist belt and was affected by high-pressure, low-temperature metamorphism. Blueschists and greenschists occur in the same outcrop and are believed to have experienced the same pressure-temperature (P-T) history which has been quantified using geothermobarometry and pseudosections for specific bulk-rock compositions. Calculated P-T conditions indicate minimum pressure of approximately 0.9 GPa and temperature of approximately 370 degrees C for the peak of metamorphism. The prograde and retrograde paths followed a very similar low geothermal gradient (10-12 degrees C/km) with cooling during decompression. Pseudosections show that both blueschists and greenschists can exist stably at the metamorphic peak, the dominant amphibole being a function of bulk composition: the blueschists, on average, have lower Mg# than the greenschists, which results in a larger P-T stability field of blue amphibole. A pseudosection analysis of the dehydration behaviour indicates that blueschists and some greenschists can preserve their peak assemblages (no dehydration along the retrograde path), whereas greenschist assemblages, in general, are rather prone to undergo dehydration and hence re-equilibration to lower P-T conditions during exhumation.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 21
Serial Issue: 1
Title: High-pressure/low-temperature metamorphism of basalts in Lavrion (Greece); implications for the preservation of peak metamorphic assemblages in blueschists and greenschists
Affiliation: National Technical University of Athens, Department of Geological Sciences, Athens, Greece
Pages: 133-148
Published: 200901
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 61
Accession Number: 2009-032672
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables, geol. sketch map
N37°38'60" - N37°45'00", E23°58'00" - E24°04'60"
Secondary Affiliation: Karl-Franzens University, AUT, Austria
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200918
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