Does ternary feldspar constrain the metamorphic conditions of high-grade meta-igneous rocks? Evidence from orthopyroxene granulites, Bohemian Massif

Abstract

The presence of ternary feldspar in high-grade meta-igneous rocks, and the recognition of the thermometric significance of this mineral, has led recent researchers to postulate peak metamorphic temperatures in excess of 1000 °C. However, it needs to be established that such ternary feldspar is not in fact a survivor of the original high-temperature crystallization of the igneous protolith. After exsolution, the host and lamellae in the ternary feldspar grains may be stable throughout subsequent history as long as recrystallization does not occur. Such a history may involve rehydration and metamorphism, including H O-saturated conditions, with the compositions and proportions of the host and ..