EVSC 2800 Study Guide - Final Guide: Feldspar, Hornblende, Calcite
12 May 2016
School
Department
Course
Professor
Document Summary
The presence of hydrothermal fluids accelerates the chemical reactions in metamorphism. Metamorphosed sedimentary rocks have become marble, schist, and gneiss. We characterize the extent of metamorphism by how high the temperatures were when metamorphic rock formed. Low grade metamorphic rocks were formed in low temperature and pressure: lowest-grade metamorphism leaves platy minerals in crystals too small to see. Foliation results in a rock that behaves like shale in its tendency to split. Shale splits along bedding planes; slate splits along foliation planes. The tendency to split is called slaty cleavage: slightly hotter low-grade metamorphism adds very thin segregated layers of different minerals and closely spaced foliation planes. The parallel arrangement of sheet minerals like mica results in pervasive foliation. This extreme foliation is called schistosity. schist is one of the most abundant metamorphic rocks types and may contain 50% platy minerals.
