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Unformatted text preview: 40 Journal of the Czech Geological Society 48/12(2003) Petrology of spinel-bearing migmatites from the Sauwald, Southern Bohemian Massif I. DEIBL 1 P. TROPPER 1 W. MIRWALD 1 F. FINGER 2 1 Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, A-6020 Innsbruck, Austria; firstname.lastname@example.org, Peter.Tropper@uibk.ac.at 2 Institute of Earth Sciences, University of Salzburg, Hellbrunnerstrasse 34, A-5020 Salzburg, Austria calculations. This yields pressures ranging from 14 kbar and temperatures of 550 °C670 °C, which are probably too low compared to the results of Knop et al. (2000) which yielded P-T conditions of 780 °C and 3.8 kbar. An important part of the evaluation of the P-T-a (H 2 O) conditions of these high-grade metapelites is the applica- tion of thermobarometric techniques involving cordierite. In recent years, an extensive evaluation of cordierite as a petrogenetic indicator in high-grade metapelites was per- formed (Mirwald and Knop, 1995; Knop and Mirwald, 2000). These studies focused on the incorporation of so- dium in cordierite as a function of temperature, pressure and a (H 2 O). Mirwald (1986) and Knop and Mirwald (1999, 2000) found an inverse correlation between the sodium content and temperature, allowing a potential application of this relation as a thermometer. Their study also showed that the incorporation of sodium into cordierite is virtually pressure-independent. Knop and Mirwald (2000) and Scheikl and Mirwald (1998) showed that the sodium con- tent of cordierite is also a monitor of the presence of fluid or melt in metapelitic rocks. Therefore, the sodium con- tent of cordierites may also serve as a monitor for a (H 2 O) in the rocks. Our data indicate temperatures of ca. 650 700 °C for the cordierite cores in the presence of a fluid...
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