Granite: Some Tectonic, Petrological, and Physico-Chemical Aspects

Abstract

AbstractGranites of the main movement-phase of an orogenic zone form an integral part of the tectonic pattern being characteristically located at the intersection of cross- and main-folds. Here, an older granitic core pierces upwards through the anticlinal vault to form a diapir-fold in which migmatization, synchronous with movement, leads to the evolution of granodiorite. At higher structural levels where pressure is lower K-granites occur. Only at sub-volcanic levels has evidence of melting been found.Recent hydrothermal investigations, by Bowen and Tuttle, show that synthetic haplo-pitchstones whichbeginto crystallize at minimum temperatures become richer in K as pressure decreases. These results are closely comparable with evidence provided by the sub-volcanic K-microgranites (migmatized Caledonian granodiorite) of Slieve Gullion, but have no application to the granodiorites.