Petrogenesis of Garnet Periodotites and Eclogites in the Bohemian Massif, Czechoslovakia

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An integrated field and laboratory investigation is planned of garnet peridotites and eclogites in the Czech portion of the Bohemian Massif, which is the easternmost extent of the Variscan Orogen in Europe. These high-pressure rocks occur in sequence of continental crustal rocks in the Moldanubian Zone, which is the most internal and highly metamorphosed tectonostratigraphic unit of the Variscan Orogen. Previous studies have demonstrated: 1) the occurrence of two types of garnet peridotites, which exhibit different modes of origin, T-p histories, and cooling rates, and 2) a mantle origin for Group A eclogite lenses in peridotites, which formed by high-pressure crystal accumulation and were carried into the crust by enclosing peridotites that were tectonically emplaced during the Variscan Orogeny. Further isotopic investigations will be performed on selected peridotite and ecologite samples that have already been characterized petrologically, and integrated field, petrologic, geochemical, and isotopic studies will be made of additional peridotite bodies and Group B eclogite lenses in gneisses. The results should provide a basis for establishing the timing and nature of high-pressure metamorphism in this portion of the Variscan belt, an improve our understanding of the complexities involved in the interaction of mantle and crust during orogenesis.