Metamorphic reaction of epidote in Alpine-type veins to garnet-anorthite symplectites: Markovice, Kutná Hora Unit (Bohemian Massif)
Abstract
The studied garnet-anorthite symplectite often preserve outer crystal shapes of the original clinozoisite-epidote crystals. It is suggested that the geological and metamorphic evolution of the local amphibolites of the Kutná Hora Crystalline Unit included the following stages:
1) the older regional metamorphism that was instrumental in alteration of mafic volcanics and tuffs into amphibolite,
2) the brittle deformation, extension and fluid activity resulted in fractures with druses of clinozoisite-epidote,
3) in the course of a younger metamorphic event, the clinozoisite-epidote reacted under reducing conditions and its dehydration led to the formation of the studied garnet-anorthite symplectites,
4) later on, already at shallow crustal levels, late-Variscan, low-temperature fluids brought about crystallization of zeolites and hydrated silicates. The temporal sequence of processes is interpreted in terms of a polymetamorphic history of the host Kutná Hora Crystalline Un