Quartz exsolution in clinopyroxene of high-pressure granulite from the Münchberg Massif
Gayk, Thomas; Kleinschrodt, Reiner; Langosch, Alexander; Seidel, Eberhard
European Journal of Mineralogy Volume 7 Number 5 (1995), p. 1217 - 1220
published: Oct 5, 1995
ArtNo. ESP147050705015, Price: 29.00 €
Abstract A slice of intermediate to acid high-pressure granulite associated with spinel lherzolite has been found within amphibolite-facies rocks of the Münchberg Massif in NE Bavaria. Calculated temperatures (garnet-clinopyroxene exchange thermometry) and pressures (GASP geobarometry) show that the granulites endured conditions of around 1.8 GPa and at least 1100 K during their evolution. Intermediate granulites with garnet (Alm45Prp30Grs25), plagioclase (An24), pargasitic hornblende, quartz and rutile contain clinopyroxene (Jd20) with oriented, lath-shaped quartz exsolutions. No additional exsolution phase was observed in the pyroxene. The quartz laths are interpreted to have exsolved from a former clinopyroxene with about 10 mol % Ca-Eskola component. This pyroxene was probably formed at about 2.5 GPa and temperatures > 1200 K. The high-pressure granulites were formed in the same pressure range as the eclogites of the Münchberg Massif, but at significantly higher temperatures. The associated spinel Iherzolite probably acted as a heat source.