1.1. -Alteration of the composition or structure of a rock by heat or pressure Types. (a) Contact metamorphism- high temp..e.g. Hornfels (b) Regional metamorphism- pressure-rocks are usually foliated, large sections of crust
2. characteristics of metamorphic rocks
2.1. 1.Foliated or Non-foliated- foliation is a texture that develops when platy or elongated minerals are aligned by different stress. 2. Mineralogy- stable minerals form under different metamorphic conditions.
3. Factors controlling the characteristics of metamorphic rocks
3.1. (a)Composition of the parent rock- e.g Sandstone(parent rock) changes into Quartzite. (b) Temperature (c) Pressure (d) Fluids- mainly hot water.
4. Classification of metamorphic rocks
4.1. (1)Foliated;- slate, phyllite, schist, gneiss. Non-foliated:- marble, Quartzite, Anthracite. (2) Grain size;- very fine to fine (slate, phyllite, anthracite). medium to coarse (schist, gneiss, marble, Quartzite). (3) Parent Rock;- Slate (Shale, mudstone or siltstone)< Phylite (slate), Schist (phylite), Gneiss (Schist, granite or volcanic rocks), Marble (Limestone, dolostone), Quartzite (Quartz, sandstone) Anthracite (Bituminous coal)>
5. Metamorphic Grade.
5.1. -Intensity of metamorphism. Order from low grade to high grade. Shale.> Slate.>Phylite.>Schist.>Gneiss.
6. a rock that has been changed by heat and/or pressure without completely melting.
