Eclogites at the north-western margin of the Bohemian Massif; a review

The eclogites and their amphibolitized derivatives in the Munchberg nappe complex are conformably intercalated within metasediments. From their major, trace and REE geochemistry, two types of eclogite can be distinguished: dark eclogites exhibit a MORB-like compsition, whereas light, commonly kyanite-bearing, eclogites are presumably derived from a high-Al gabbroic protolith, in part plagioclase-rich cumulates. The stable assemblage kyanite + omphacite (jd < than or = to 50 mole %) indicates P > 20 kbar in the 600-650 degrees C range. Radiometric dating points to a minimum age of 395 m.y. for the final stage of the high-P event. Isothermal uplift led to various breakdown assemblages; a penetrative medium-P overprint at approx 380 m.y. transformed the eclogites to garnet amphibolites. Mineral assemblages in the interlayered metasedimentary host rocks indicate P 5-6 kbar and T 550-650 degrees C for this amphibolite- facies metamorphism. Among the various occurrences of eclogitic relics in the Moldanubicum the retrograded eclogite body at Winklarn is the most pominent. It is associated with peridotites and garnet pyroxenites and intercalated with Moldanubian cordierite-sillimanite gneisses. According to the record in the metabasites, the P-T evolution probably started in the amphibolite facies and continued through the eclogite (710 degrees C, > than or = to 15 kbar), high-P granulite(800 degrees C, 12 kbar), medium- P granulite (700 degrees C, 7-9 kbar) and low-P amphibolite facies. This latest overprint is dated at 2330 m.y.