EESC1180 Lecture Notes - Lecture 9: Mylonite, Gneiss, Metamorphic Facies
5 Oct 2017
School
Department
Course
Professor
Document Summary
Rocks that are changed from pre existing rocks deep within the earth through heat, pressure, differential stress and hydrothermal fluids. Changes in mineral composition and texture of a rock. A bent layer or series of layers that used to be horizontal and became deformed. 100-2-- d celcius or 1000 atmospheres pressure. Crystal foliation is usually wavy or distorted. Grains deform without breaking and become aligned in a perpendicular to direction of forces. Grains slide sideways and cause flattened and deformed grains. Fusing of grains and enlargement of crystal size - hardness stays the same. Chemistry of original mineral stays the same, but crystals fuse together. Growth of new mineral crystals that are different. Stress that is greater in one direction. Direction of preferred orientation - right angles to max compression axis. Metamorphism takes place in response to changes in temp, pressure or shear or hydrothermal fluids. Parallel planar fabric common to many metamorphic rocks.
