Metamorphism and METAMORPHIC Rocks Flashcards
These rocks have altered fabric form the parent rock by different mineral sizes, arrangements, and textures.
metamorphic rocks
process of transforming minerals and structures of rocks involving heat and distortion, together or separately.
metamorphism
2 types of metamorphism
regional and contact
5 main factors of metamorphism
Parent rock mineral fabric
Temperature
Pressure
Fluid availability (usually water)
Time
considered to be the igneous or sedimentary rock origin of the metamorphic rock
parent rock
affects the texture and cause foliation
pressure
same pressure from all directions
equal confining pressure
side pressure higher than top and bottom pressure
directed pressure
pressure pushes sides in opposite directions
shear stress
same composition different crystal structure
polymorphs
other 2 types of metamorphic rocks
foliated and non-foliated
directed pressure / shear stress
foliated
no to little pressure
non-foliated
the “layering” or “banding” in metamorphic rocks causing “sheet-like” structure
foliation
4 classifications of foliated rocks
slaty, phyllitic, schistose, gneissic
From low-grade metamorphism of shale.
Microscopic clay and mica crystals have grown and aligned perpendicular to the largest stress.
Breaks into very thin flat sheets along cleavage using a chisel
slaty
Similar to slate but heated to a higher temperature
Has larger mica crystals but still barely visible to the eye as sheen on the surface
Can form in wavy / silky / crenulated layers
phyllite
High enough temperatures forming mica big enough to be seen by the naked eye, possibly with quartz, feldspar, etc. visible.
Strongly foliated and often bonded with coarse crystals.
schist
Minerals have been separated into distinct bands
Dark bands are usually biotite and hornblende and light bands are quartz and feldspar.
Foliation is not as intense as schist.
gneiss
Form in areas where pressure is just confining pressure (same pressure from all sides) or low-pressure conditions.
Mostly, these rocks are not buried deep enough and the heat is coming from a nearby body of magma.
non-foliated rocks
the difference of a material’s property at
different directions.
anisotropy
