Stable association wollastonite-anorthite,and other cale-silicate assemblages in amphibolite-facies crystalline schists of Nanga Parbat,Northwest Himalayas

Progressive regional metamorphism and granitization of a dominantly pelitic sequence was essentially isobaric and proceeded on a level of rather high P within the field of amphibolite facies. The transition from kyanite to sillimanite zone does not coincide with the boundary between medium- and high-grade rocks but is displaced toward higher T. Many of the Al-Si-rich high-grade rocks carry stable muscovite. Staurolite, andalusite, and cordierite are characteristically absent. Green hornblende occurs throughout the high-grade zone in rocks of appropriate composition. Calcareous intercalations permit recognition of three distinct zones of high-grade metamorphism. They, and the reactions defining their boundaries, are

1. 1.
   ?Wollastonite-anorthite zone”; highest grade attained a) Ca₃Al₂Si₃O₁₂ + SiO₂ ? 2 CaSiO₃ + CaAl₂Si₂O₈