Abstract

Granulite facies metamorphic events are constrained commonly through application of U-Pb zircon geochronometry. Zircon growth related to high-grade metamorphism is interpreted as reflecting the age of peak pressure-temperature (P-T) conditions. However, these ages obtained from granulites need to be interpreted with considerable care. Under conditions of high-grade metamorphism, it is important that the possible presence of melt is considered. Our modeling of partial melting and its impact on zircon stability implies that zircon crystallization in hot, isothermally uplifted granulites could postdate the pressure peak of the P-T path. In a case study of felsic granulites from the Bohemian massif of Variscan central Europe, it appears likely that most zircons in the rocks would have grown after they were exhumed to medium pressure levels. Thus, zircon growth related to high-grade metamorphism should not be automatically assumed as reflecting the age of peak P-T conditions.

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