Metamorphism Flashcards
The most important driving factor for metamorphism
heat
Why is heat the most important factor for metamorphism?
Provides the necessary energy to enable chemical reactions that change mineral stability.
Recrystallisation
When minerals restructure themselves in order to adapt to increasing temperatures, creates whole new minerals, new structures, same compostition.
Subsiding Basin
Where deeply buried sedimentary strata is metamorphosed
Environments where rocks may be carried to great depths and heat include ______, where slabs of sediment laden oceanic crust are subducted
Convergent Plate Boundaries
Confining Pressure
Forces that are applied equally in all directions. Packs grains together increasing their density. recrystallises minerals. does not fold.
Differential Stress
Greater in one direction than others.
Shortened in the direction of greatest stress.
Elongated in the direction perpendicular to the stress.
Rocks involved are folded or flattened. Causes Anticline and Synclines.
Why are chemically active fluids relevant?
Enhance migration of ions, aiding in recrystallisation of minerals.
Contact Or Thermal Metamorphism
rocks immediately surrounding a molten body are baked and temperatures cause rocks to metamorphose.
Hydrothermal Metamorphism
Chemical reaction caused by ion rich fluid that flows into the cracks of rock, causing it to recrystallise. Alteration of chemical structure of a rock is also called Metasomatism
Burial Metamorphism
Massive amounts of sediment or volcanic material accumulate in a basin, the pressure causes them to metamorphose
Subduction Zone Metamorphism
Rocks are carried to great depths along subducting plates in a convergent plate boundary environment.
Regional Metamorphism
Most metamorphic rock is produced during mountain building when large segments of the earth crust are deformed along convergent plate boundaries. Mostly occur during continental collisions.
Prograde Vs Retrograde metamorphism
Prograde- meta as rocks move to high grade conditions high temp and pressure
Retrograde- meta as rocks move to low grade conditions
Foliation
Textured metamorphism. Can occur because of differential stress, visible directional stress.
