EARTHSC 1G03 Lecture Notes - Lecture 6: Phyllite, Schist, Migmatite
5 Apr 2017
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Document Summary
Metamorphic rocks: have been changed mineralogically and/or texturally through heat, pressure or fluids. Provide a window into past temperatures, pressures and fluid composition. Unlike igneous and sedimentary processes, we can"t see metamorphic rocks forming naturally. Metamorphism occurs at pressures (p) and temperatures (t) well above those on. Earth"s surface but below p and t conditions that cause melting (often in the deep crust) Compression causes alignment of elongated or platy minerals and growth of new minerals in same direction= foliation. Usually associated with plate collisions (subduction zones) Elgonated and plated minerals aligned and compressed. Micas start growing perpendicular to stress along cleavage planes. Coarser than phyllite, will break along cleavage planes. Minerals segregated into light (quartz and feldspar) and dark (biotite and amphibole) bands. Coarser than schist, won"t break along cleavage planes. Partial melting in the core of mountain belt. Mixture of igneous (granite) and metamorphic (gneiss) rock.
