Quartz pseudomorphs after coesite in eclogites from the Saxonian Erzgebirge
European Journal of Mineralogy Volume 3 Number 2 (1991), p. 231 - 238
published: Apr 18, 1991
manuscript accepted: Oct 26, 1990
manuscript received: Apr 30, 1990
ArtNo. ESP147050302003, Price: 29.00 €
Abstract Eclogites are intercalated in gneisses in the central and western Erzgebirge. Petrographically, they show a regional zonation from E (FlÖha Syncline) to W (Oberwiesenthal) with respect to the primary mineralogy, retrograde reactions and textures. Probable quartz pseudomorphs after coesite are described as inclusions in omphacite and garnet in the FlÖha Syncline rocks. New data are given on the composition of the eclogite assemblage. For the FlÖha Syncline eclogites, geothermobarometry indicates an equilibrium at about 700-800°C and ≥ 13-16 kbar with the higher temperature values in the east. A significantly lower temperature (about 650°C) was obtained for an eclogite from the Oberwiesenthal area. Some aspects contribute to an "m situ" model rather than a "foreign" one at least for the high-temperature eclogites of the FlÖha Syncline. The present results suggest that nappe tectonics is an essential feature in the geological evolution of the Erzgebirge whereas an overthrusting towards the west is favoured.