(C) Metamorphic Rocks • Metamorphic rocks are formed deep within the earth by the transformation of any pre-existing rocks in the solid state by heat, pressure or both. The composition, mineralogy, texture or structure of the rock will be changed. • Metamorphism will lead to the development of new textures and minerals due to: - Deformation and reorientation of their mineral composition. Recrystallization of minerals into larger grains. Chemical recombination leading to the formation of new minerals. • Types of metamorphism: - Dislocation metamorphism (Fault-zone metamorphism) Relative movement of rocks along the fault zone may cause the rocks to be severely stressed, crushed and fragmented. Increase in temperature due to frictional heating (except very large faults) Thermal metamorphism (Contact metamorphism) Localized effect; occur near the contact of plutons which are hotter than the country rocks, causing the adjacent rocks to be metamorphosed. Formation of metamorphic aureole:
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