Metamorphic Rocks Flashcards
the change undergone by an existing rock (e.g., igneous, sedimentary or metamorphic), in the solid state, to another rock
Metamorphism
Agents of Metamorphism
heat, pressure, chemically active fluids
Sources of Heat
Geothermal Gradient - temperature increases with depth (20° – 30°C per km in the crust)
Large bodies of molten rock or intrusive bodies
Provides the energy to drive chemical reactions → _______________ of minerals
recrystallization
Type of Pressure:
compression in ALL directions
Confining
Type of Pressure:
causes chemical reactions; leads
to smaller, denser packets
Confining
Type of Pressure:
compression in ONE direction
Directed
Type of Pressure:
leads to foliation
Directed
Sources of Fluids
Water trapped in pore spaces of the original rock
Water from magmatic bodies (hydrothermal fluids)
Type of Metamorphism:
occurs when magma invades pre-existing rock
Contact
Type of Metamorphism:
takes place at shallow depths (0-6km) and low pressure
Contact
Type of Metamorphism:
forms non-foliated rocks
Contact
In contact metamorphism, a zone of alteration called an _____ (or halo) forms around the emplaced magma
aureole
Type of Metamorphism:
takes place at considerable depths over an extensive area (5-30 km)
Regional
Type of Metamorphism:
under high pressure; associated with mountain building
Regional
Type of Metamorphism:
forms foliated rocks
Regional
Type of Metamorphism:
chemical alteration at high temperatures and moderate pressures by hot, ion-rich (hydrothermal) fluids that circulate through fissures and cracks
Hydrothermal
Type of Metamorphism:
common in basaltic rocks
Hydrothermal
Type of Metamorphism:
form rich ore deposits
Hydrothermal
Classifications of Metamorphic Rock:
Texture
Protolith
Mineralogy
Texture:
exhibits a pervasive planar structure due to the nearly parallel alignment of minerals and/or compositional and mineralogical layering in the rock
Foliated
Texture:
no preferred mineral orientations; metamorphism leads to transformation of one mineral to another
Non-foliated
original rock that undergoes metamorphism to form other rocks in a geological setting, influenced by processes such as mantle partial melting and reactions with continental crust components
Protoliths
