Reactions behaviour during kelyphite and symplectite formation; a case study of mafic granulites and eclogites from the Bohemian Massif
Reactions behaviour during kelyphite and symplectite formation; a case study of mafic granulites and eclogites from the Bohemian Massif
European Journal of Mineralogy (February 1990) 2 (1): 125-144
- Austria
- Bohemia-Moravia System
- Bohemian Massif
- Central Europe
- Czechoslovakia
- eclogite
- electron probe data
- Europe
- granulites
- intergrowths
- mafic composition
- metamorphic rocks
- mineral assemblages
- North Austrian Crystallines
- petrography
- petrology
- reaction rims
- symplectite
- kelyphite
- Aggsbach
- Nove'Dvory
- Borek Quarry
The regression of these high-grade metamorphic assemblages takes place by the development of coronite rims between garnet and pyroxenes, symplectite replacements after sodic pyroxenes and kelyphite overgrowths on garnet. The garnet may show an outer coronitic reaction boundary and an inner kelyphitic rim. The retrograde P-T path was dominated by a decrease in P. The trajectory may be characterized initially by an increasing T during the completion of the corona-forming reaction; the later retrograde path is characterized by slight undercooling during symplectite formation and then by an increase in undercooling which occurred during kelyphite formation. The equilibration rate was shown in retrograde anhydrous assemblages and these rocks preserve widespread relics of climax conditions. In the hydrous assemblages, the presence of water enhanced the reaction rate, enlarging the reaction domains.