Rock-forming and accessory minerals during retrogression of high-grade metamorphic and metamagmatic rocks from orogenic belts.
Investigators from institution:
Igor Broska, Marian Janák, Milan Kohút
Subduction of rocks in orogenic belts followed by exhumation is manifested by re-equilibration of mineral associations first to adapt to ultrahigh-pressure (UHP) conditions of eclogite facies, then to the conditions of lower pressure but high temperature granulite facies. Re-equilibration may almost fully obliterate previous UHP history, however, some accessory minerals and inclusions in garnet still witness previous high pressure. Project is oriented to finding, identification of such minerals, diamonds, fluid inclusions, Ca-rich garnet relics, phengites, (U)HP monazites, which can be chemically dated. We shall study mostly diamond-bearing rokcs from the Caledonides (Sweden, Norway), i.e. the orogenic belt, which has not experienced any subsequent orogeny. On the contrary, Western Carpathians, rocks of the northern Veporic zone, recorded three orogens, Ordovician, Variscan and Alpine (Cretaceous) and represent a challenge – to distinguish these events according to the ages and metamorphic degree.