Lecture 13 Flashcards
(24 cards)
What are metamorphic rocks?
Result of transformation of preexisting rocks into new rocks. (remain in solid state)
What are the types of changes that rocks can undergo>
Textural and mineralogical (most of the time it’s both!)
What are textural changes
Minerals rearranging themselves
Wht are mineralogical changes?
New minerals coming in.
Why do rocks change?
Because they must remain in equilibrium with the environment-if the environment changes, then the rock changes.
How does Granite undergo metamorphisis?
Granite is an igneous rock found on the surface. Sinks back into Earth and changes into Gneiss (metamorphic rock), using textural changes. Gneiss continues to be buried and the minerals melt, energy decreases, minerals segregate and turn into Migmatite
What is Migmatite?
A metamorphic rock that shows the process of melting-is the halfway point between an igneous rock and melting
How is marble formed?
Through the calcite recrystallization of limestone (sedimentary rock)
What is the economic significance of studying metamorphic rocks?
They make up slightly more than 1/2 of mineral ores on earth. Can look at succession of transformations into Earth’s interior
What are the 3 major types of metamorphism?
Regional (Barrovian) and Contact (Buchan)-most common, Burial
What is regional metamorphism?
Pressure in different raised areas of Earth fracture rocks in different ways
What is Contact metamorphism?
Magma reaches surface. Dissipation of heat through surrounding environment. Transforms preexisting rocks (TEMPERATURE IS MOST IMPORTANT FACTOR)
What is Burial metamorphism?
Depression zones in which sediments are transported and begin burial process and metamorphism. Have to have a very high rate of sediment addition (close to mountains).
What is low grade metamorphism?
Temp and pressre increase and slight affect by metamorphism
What is medium and high grade metamorphism?
Burial continues, pressure and temp increase
What are high grade metamorphic rocks?
Mid point of medium grade and igneous rock (molten)
What are the 2 textures of metamorphic rock?
Foliated and non
What are foliated (schistose) rocks?
Rearrangement of minerals, looks like lines (preferential orientation
What are Non-foliated rocks (granoblastic)
Have a non-preferential alignment.
What is rock cleavage?
Tendency of the rock to break along parallel or sub-parallel surfaces. Textural alignment of mineral grains or subparallel arrangements of discontinuities.
What is slaty cleavage?
Low grade metamorphic rocks. Beginning of burial-can still recognize original rocks. Can tell from what rock it was formed. Fossils occur here.
What is phyllite cleavage or foliation?
Medium grade rocks. Original alignment lost, fossils almost destroyed
What is Schistose foliation?
Medium grade rocks. Surfaces of cleavage, bright, reflect light easily. Most frequent metamorphic rocks. Most of Canadian Rockies
What is Gneissic foliation?
High grade, partial melting
