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Physical Geology (plummer, carlson, hammersley 13th 2010)
chapter 7
23
Geology
Graduate
11/18/2011

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Term
Metamorphism
Definition
The changes that occur to a rock within the Earth's interior
Term
Metamorphic rock
Definition
A rock with altered texture and/or mineral assembly due to metamorphism
Term
Parent rock
Definition
The original rock before it underwent metamorphism
Term
Ductile (Plastic)
Definition
Capable of being bent and molded
Term
Four factors controlling the characteristics of metamorphic rocks
Definition
(1) Composition of parent rock
(2) Temperature and pressure during metamorphism
(3) Effects of tectonics
(4) Effects of fluids (such as water)
Term
Geothermal gradient
Definition
Temperature of a rock versus a given depth
Term
Stable minerals
Definition
A mineral is stable if it does not react with another substance or convert to another mineral over time
Term
Confining pressure
Definition
Pressure applied equally on all surfaces of a substance as a result of burial or submergence
Term
Hydrostatic versus lithostatic pressure
Definition
Pressure at water depth versus pressure at depth of burial, respectfully
Term
Stress
Definition
Force per unit area on an object
Term
Shear versus compressive
Definition
Shear is stress parallel to the planes of an object while compressive stress is perpendicular inward
Term
Dynamic metamorphism
Definition
Metamorphic rocks created through shear stress during faulting (tectonic movements)
Example: mylonite (formed from pulverized rock in a fault zone)
Term
Foliation
Definition
Refers to a rock with a planar texture, such as shale
Term
Slaty Cleavage
Definition
A pervasive, parallel foliation (layering) of fine-grained platy minerals in a direction perpendicular to the direction of maximum stress
Ex: slate and phyllite
Term
Schistosity
Definition
The layering in a coarse grained, crystalline rock due to the parallel arrangement of platy mineral grains, such as muscovite and biotite
Term
Gneissic
Definition
The layering in a rock in which bands or lenses of granular minerals (quartz and feldspar) alternate with bands or lenses in which platy (mica) or elongate (amphibole) minerals predominate
Term
Effect of water on metamorphism
Definition
Water moves between grains under high pressure, dissolves ions from one mineral, and carries those ions to a second mineral
Term
Schist
Definition
A foliated schistose rock formed under a particular pressure and temperature, which exhibits visible platy or elongate parallel-oriented minerals

Term
Contact metamorphism
Definition
Metamorphism in which high temperature is the dominant factor (usually less than 10 km below surface with relatively low lithostatic pressures). "Baking" of country rock adjacent to an intrusive contact
Term
Aureole
Definition
Zone in which contact-metamorphism occurs
Term
Regional metamorphism
Definition
Lithostatic pressure is the main driving force of metamorphism (deeper than 5 km). Usually produces foliated metamorphic rocks
Term
Index mineral
Definition
Used to determine the pressure and temperature combination under which a rock recrystallized
Term
Migmatite
Definition
A mixed igneous and metamorphic rock located at the threshold between fully igneous and fully metamorphic
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