geology metamorphic
What provides the heat and the hot caustic fluids needed to form a non-foliated metamorphic rock?
A body of magma.
What is a porphroblast?
A large, visible cystal surrounded by smaller visible crystals.
What two changes may occur to rocks as they are metamorphosed?
A rock's minerals may change, or its texture may change.
What kind of rock will form if this occurs?
An igneous rock
What kinds of rocks can be metamorphosed?
Any kind of rock can be metamorphosed
Understand where and how burial metamorphism occurs
Burial Meta: on continental shelves - occurs as sediments are deeply buried by additional sediments - burial = pressure = higher temps = low grade metamorphism - some slate.
1. What is metamorphism?
Changes to a rock's MINERALS and/or its TEXTURE without melting the rock.
What provides the directed pressure required to form a foliated metamorphic rock?
Collisions between plates along convergent plate boundaries
Understand where and how contact metamorphism occurs
Contact Meta: along contact between magma & host rx: "Baked Zone" - heat & hot caustic fluids from magma flow into host rx and cook them - nonfoliated rx like marble, quartzite, and skarn.
What 2 agents of metamorphism generate foliated metamorphic rocks?
Directed pressure & heat.
. What drives metamorphism?
Earth's Internal Heat Engine - Plate tectonics.
What are the two types of metamorphic rocks?
Foliated and non-foliated.
What 2 agents of metamorphism create non-foliated metamorphic rocks?
Heat & hot caustic fluids
What are the 3 agents of metamorphism?
Heat, directed pressure, & hot caustic fluids.
Understand where and how hydrothermal metamorphism occurs
Hydro-T Meta: at DPB (mid-ocean ridges) - occurs as sea water sinks along faults, is heated by magma to become a hot caustic fluid - HCF rise to saturate rx along the DPB - low grade meta - greenstone/serpentinite.
Why are index minerals beneficial to geologists?
Index minerals indicate the metamorphic grade of the rock
What happens if the metamorphic rock GNEISS continues to be heated?
It will melt and form magma.
At what depths within the crust does metamorphism occur?
Metamorphism occurs at depths below 2 miles within the crust.
. What is an index mineral?
Minerals that crystallize only within a narrow range of temperature and/or pressure
What does "re-crystallization" refer to?
Re-crystallization occurs when a rock's crystals grow larger or new minerals grow in the rock during metamorphism.
Understand where and how regional metamorphism occurs
Regional Meta: in the core of a growing mountain range - plate collision generates directed pressure - forms foliated rx - low, medium, and high grades depending on depth below surface - slate, phyllite, schist, gneiss.
What is FOLIATION?
The alignment of the rock's crystals
What does the term "Metamorphic Grade" mean?
The temperatures & pressures the rock experienced during metamorphism
What is the difference between low, medium, and high grade metamorphic rocks?
The temperatures & pressures under which they formed differ: low grade rx form at low temps closer to the Earth's surface, medium grade rocks from at higher temps deeper in the crust, and high grade rx from at the highest temps and deepest levels within the crust.
What does the term "Parent Rock" mean?
The type of rock that the metamorphic rock was PRIOR to metamorphism
. Why are porphroblasts important?
They are index minerals.