Partially retrograded eclogites of the Münchberg Massif, Germany: records of a multi-stage Variscan uplift history in the Bohemian Massif

摘要: Eclogites with a wide range in bulk composition are present the Munchberg Massif, part of Variscan basement Bohemian Massif north-east Bavaria. New analyses primary phases garnet, omphacite, phengite and amphibole, as well secondary clinopyroxene II, various amphiboles, biotite/phlogopite, plagioclase, margarite, paragonite, prehnite pumpellyite, reveal complex uplift history. discoveries were made samples very jadeite-rich omphacite symplectite albite. Various geothermobarometric techniques, together thermodynamic databases (incorporating separately determined activity–composition values) experimental data have clustered minimum conditions for assemblages to P–T 650 ± 60° C, 14.3 1 kbar. However, jadeite (in omphacite)–kyanite–paragonite phengite) zoisite–grossular garnet)–kyanite–quartz relationships suggests pressures 25–28 kbar at same temperatures. The fact that omphacite–plagioclase assemblage yields within few hundred bars plagioclase-free strongly values serious underestimates. Zoning, inclusion suites breakdown reactions phases, addition new minerals formed during uplift, define polyphase metamorphic evolution which, from geochronological evidence, occurred solely cycle. other eclogites distinct variation their temperatures suggest multi-stage thrusting model regional eclogites. Such an has significance respect incorporation mantle slices into crustal sequences fluid derivation successively subducted units, possibly driving reactions.