Abstract
Summary Lenses and pods of mafic rocks from the Monotonous Unit near Svetlik are characterized by eclogite facies mineral assemblages; however some inclusion patterns (oriented quartz rods in clinopyroxene and cuboids of disordered graphite in garnet) that are usually known from ultra-high pressure rocks were also observed in one sample. Conventional thermobarometry yielded maximum P–T conditions of 2.0–2.5 GPa and 750 � C. Decompression and heating at amphibolite and granulite facies conditions resulted in the formation of at least five distinct types of symplectites. These include symplectitic intergrowth of ilmenite and clinopyroxene after titanite, described here for the first time from the Moldanubian Zone. In addition, symplectites of plagioclase and biotite with accessory amounts of spinel after tabular pseudomorphs (after phengite?) are also reported here. Mass balance relations indicate that symplectites of diopside þ plagioclase after omphacite and plagioclase þ spinel (sapphirine) after kyanite þ garnet, formed by nearly isochemical reactions. All other symplectite-forming reactions were allochemical and were accelerated by the presence of fluid in the primary phases. Preserved zoning pattern in garnet with high compositional gradient in some samples suggests that the rocks were affected briefly by granulite facies overprint.
Published Version
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