metamorphic rocks (8) Flashcards
Parent Rock
The rock from which a metamorphic rock formed
Metamorphism
The changes in mineral composition and texture of a rock subjected to high temperature and pressures within Earth
Metamorphic Grade
Degree to which a metamorphic rock changes from temperature and pressure
Recrystallization
The formation of new mineral crystals in a rock that tend to be larger than the original crystals
Geothermal Gradient
The gradual increase in temperature with depth in the crust. The average is 30degrees C/km in the upper crust
Confining Pressure
Stress that is applied uniformly in all directions
Differential Stress
Forces that are unequal in different directions
Compressional Stress
Differential stress that shortens a rock body
What are four agents that drive metamorphism?
Heat
Confining Pressure
Chemically Active Fluids
Differential Stress
This agent of metamorphism is most important?
Heat
What characteristic of a metamorphic rock is determined primarily by its parent rock?
Composition
Texture
The size, shape, and distribution of the particles that collectively constitute a rock
Foliation
A term for a linear arrangement of textural features often exhibited by metamorphic rocks
Solid-State Flow
The solid-state flow of rock that occurs when rocks are exposed to extreme conditions of heat and pressure
Rock Cleavage
The tendency of rocks to split along parallel closely spaced surfaces. These surfaces are often highly inclined to the bedding planes in the rock
Salty Cleavage
A type of foliation that is characteristic of slates, in which there is parallel arrangement of fine-grained metamorphic minerals
Gneissic Texture
A texture of metamorphic rocks in which dark and light silicate minerals are separated, giving the rock a banded appearance
Nonfoliated
Describes metamorphic rocks that do not exhibit foliation
Porphyroblastic Texture
A texture of metamorphic rocks in which particularly large grains (porphyroblasts) are surrounded by a fine-grained matrix of other minerals
Slate
Foliated, fine grained, excellent rock cleavage (salty)
Phyllite
Foliated, fine grained, glossy sheen
Schist
Foliated, medium-to-coarse grained, micas dominate
Gneiss
Foliated, coarse grained, banding of dark and light
Marble
Nonfoliated, medium-to-coarse grained, soft
Quartizite
Nonfoliated, medium-to-coarse grained, hard, quartz
Hornfels
Nonfoliated, fine grained, tough, dark
Contact Metamorphism
Changes in rock caused by the heat from a nearby magma body
Aureole
A zone or halo of contact metamorphism found in the country rock surrounding an igneous intrusion
Hydrothermal Metamorphism
Chemical alterations that occur as hot, ion-rich water circulates through fractures in rock
Burial Metamorphism
Low-grade metamorphism that occurs in the lowest layers of very thick accumulations of sedimentary strata
Regional Metamorphism
Metamorphism associated with large-scale mountain building
Impact Metamorphism
Metamorphism that occurs when meteorites strike Earth’s surface
What are 3 rocks that are produced by contact metamorphism?
Hornfels
Quartzite
Marble
What is the agent of hydrothermal metamorphism?
Hot water full of dissolved ions
Which type of plate boundary is associated with regional metamorphism?
Convergent
Index Mineral
A mineral that is a good indictor of the metamorphic environment in which it formed. Used to distinguish different zones of regional metamorphism
Migmatite
A rock exhibiting both igneous and metamorphic rock characteristics. Such rocks may form when light-colored silicate minerals melt and then crystallize, while the dark silicate minerals remain solid
Metamorphic Facies
A group of associated minerals that are used to establish the pressures and temperatures at which rocks undergo metamorphism
