GLG 301 Lecture Notes - Lecture 4: Blueschist, Depositional Environment, Radiometric Dating
Document Summary
Rocks formed by placing pre-existing rocks under pressure and/or temperature (also by hot fluid flow) Often associated with plastic deformation and reorientation or recrystallization of minerals into gneissic foliation (planar structures due to mineral alignment) Metamorphism changes in the minerals present and their orientations due to heat, pressure, or chemical changes due to fluids (metasomatism). Contact metamorphism (metamorphism of a rind in contact with hot/molten material. What you get depends on what you start with (protolith original rock) Pressure will re-orient (and align) mineral growth or deform pre-existing ones (often flattens grains) Metamorphic grade refers to the amount (degree) of metamorphism (dependent on increasing p and t: metamorphic grades are defined by characteristic minerals that are present. Low p, t conditions result in chlorite or serpentine, resulting in. High p conditions produce a blueschist due to a variety of amphibole. Actual mineralogy depends on the minerals in the protolith.
