Upper-amphibolite Facies Conditions Research Articles

Fluids and melting under upper amphibolite facies conditions

Internal buffering paths on temperature-water activity diagrams for the pelitic model system: NaAIO 2 - KAIO 2 - CaAI 2 O 4 - Al 2 SiO 5 - SiO 2 - H 2 O give rise to sequences of assemblages which correspond to those observed in upper amphibolite facies terranes. In particular, the persistence of the assemblage quartz-alkali feldspar-plagioclase-muscovite-sillimanite across a zone and the rapidly changing composition of plagioclase across this zone can be accounted for in a natural way.

Kornerupiue in metasomatic zones, Strangways Range, Central Australia

SummaryThe first known occurrence of kornerupine in Australia is described. The mineral is a minor component of a phlogopite-rich garnet-corundum-spinel metasomatic zone, which cuts mafic and ultranlafic spinel-plagioclase-orthopyroxene-hornblende rocks. The kornerupine-bearing assemblage was formed during the second major metamorphic episode that affected the terrain, probably under low-grade granulite or upper amphibolite facies conditions. Kornerupine appears to have formed at significantly lower levels ofP-Tthan those reached in the terrain during the peak of the second granulite metamorphism.