Geology - Metamorphism Flashcards
Metamorphism
The process physical/chemical weathering of rocks with morphological changes.
What changes occur from metamorphism?
Chemical composition, mineraology and texture until temperature/pressure equilibrium reached.
Where does metamorphosis occur?
10-30km deep and surfaces.
Where is metamorphism primaritly?
mid-low crust due to heat and pressure by Earth interior.
Metamorphic Grade
Describes the temperature and pressure conditions where metamorphic rocks form
What does metamorphic grade increase with?
Pressure/Temperature
How does heat transform rock?
Breaking chemical bonds, recrystallising atoms and molecules when surface rocks transported to depths.
Geothermal Gradient
The rate of temperature change with increasing depth in Earths interior.
Types of pressure rocks experience…
Confined
Directed
Confined Pressure
This is applied equally in all directions, increasing with depth with overlyign mass.
Directed Pressure
Exerted in a particular direction, as in the convergence of lithospheric plates.
Hydrothermal fluids affect on metamorphosis…
Accelerate metamorphosis chemistry, dissolving soluble chemical substances like Na, K and CO2.
Types of metamorphism…
Regional
Contact
Seafloor
Shock
Hydrothermal Fluids
These are hot groundwaters circulating within Earths crust.
Regional Metamorphism
Occurs where there are high temepratures/pressure over large parts of the crust.
Contact Metamorphism
Where igneous intrusions metamorphose a rock immediately surrounding it.
Seafloor Metamorphism
Is associated with mid-ocean ridges most often, hot basaltic lava spread heats sea water that infiltrates, with convection occuring through the new foreign crust.
Shock Metamorphism
Collision of meteorites with Earth where energy transmits heat and shock waves to the rock, potentially producing tekties.
Foliation
These form from directed pressure/temperature deforming igneous and sedimentary rocks.
Lowest grade of foliation…
Slate
Phyllites
Higher metamorphic grade than slate, glossier containing mica and chlorite, split in sheets
Schist
Schiscosity derives from high temperatures and pressure subjected onto minerals, where they become more visible and segregate into lighter and darker bands.
Gneiss
Have dark and light coloured bands from segregation of amphiboles and quartz/feldspar
Migmatite
Mix of igneous and metamorphic rock resulting from partial metling of gneiss.
Granoblastic
Rocks with coarse granular appearnace produced by recrystallisation in metamorphism
Porphyroblasts
Large crystals having grown in a metamorphic rock
Crystallisation
The process where a fluids atoms allign in chemical proportions/arrangements to form a solid substance.
Example of a crystal…
Diamond of carbon tetrahedra bound together.
