Metamorphism
The transformation of one rock into another by temperatures and/or pressures unlike those in which the original rock formed.
Metamorphic rocks can be produced from.. (3 things)
Igneous rocks
Sedimentary rocks
Other metamorphic rocks
Metamorphic rock cannot melt but undergoes changes is... (2)
Viscosity
Crystallography
Viscosity
loss of cohesion between crystals/grains
Crystallography
atomic arrangement within crystals
Agents of Metamorphism (3)
Heat
Pressure
Chemically active fluids
Contact or Thermal metamorphism
A type of metamorphism that results from intrusion of magma into a host rock
Hydrothermal metamorphism
A type of metamorphism that happens as a result of chemical alterations from hot, iron-rich water
Regional metamorphism
A type of metamorphism that occurs during orogenesis; produces the greatest volume of metamorphic rock; usually displays zones of contact and/or hydrothermal metamorphism
Heat (as an agent of metamorphism)
Agent comes from ____ in magma and an increase in temperature with depth due to the geothermal gradient.
Pressure (as an agent of metamorphism)
An agent of metamorphism that can be isotropic or anisotropic.
Isotropic
Confining pressure applies forces equally in a ll directions and increases with depth
Anisotropic
Unequal pressure in different directions; induces differential stresses or shear stresses.
Chemically active fluids (as an agent of metamorphism)
Mainly water with other volatile components; enhances migration of ions; aids in recrystallization of existing minerals
Sources of chemically active fluids (3)
Pore spaces of sedimentary rocks
Fractures in igneous rocks
Hydrated minerals such as clays and micas
The importance of parent rock
most metamorphic rocks have the same chemical composition as the _________________ from which they formed.
Texture
The size, shape, and arrangement of mineral grains
Two types of metamorphic texture
Foliated
Non-foliated
Foliation
Any planar arrangement of mineral grains or structural features within a rock
Examples of foliation (3)
parallel alignment of flattened mineral grains and pebbles
Compositional banding
Rock cleavage
Ways foliation can form (3)
Rotation of platy and/or elongated minerals
Recrystallization of minerals in a preferred orientation
Changing the shape of equidimensional grains into elongated shapes that are aligned or rotated
Foliated Textures
The texture that results from differential stresses
Non-foliated Textures
The texture that results from confining pressure
Types of Foliated Textures (4)
Slaty parting
Schistocity or Schistos
Gniessic banding
Augen
Types of non-foliated textures
Fused Granular Texture (most common)
Prophyroblastic Texture
Eclogitic Texture
Common Metamorphic Rocks in the continuum with increasing pressure & temperature going down.
Sediment
Sedimentary Rock
Foliated metamorphic rocks
____ is formed from sediment.
Clays
_____ is formed from sedimentary rock.
Shale
4 types of foliated metamorphic rocks
Slate
Phyllite
Schist
Gneiss
Slate
A very fine-grained foliated rock with excellent cleavage; generated from shale; platy minerals not large enough to be see with an unaided eye.
Phyllite
Made of small platy minerals; glossy sheen & wavy surfaces; contains fine crystals of muscovite and/or chlorite micas
Schist
Medium to course grained; made of mainly platy minerals (micas)
Gneiss
Contains medium to course-grained grains; banded/warped appearance; high-grade metamorphism; often white or light-colored feldspar with bands of dark ferromagnesian mineras
Fused Granular Texture (4 types)
Quartzite
Argylite/Hornfels
Marble
Anthracite
Quartzite
A nonfoliated rock; formed from quartz-rich sandstone; quartz grains are fused together giving it a feathery/overlapping appearance
Argylite
A nonfoliated rock; formed from a predominantly clay parent rock (shale); tightly fused fine-grained metamorphic rock; so small you can't see
Marble
Coarse; crystalline; parent rock was limestone or dolostone; used as a monument stone; PROBLEM: dissolves with a weak and small amount of acid
Anthracite Coal
formed from plan matter; highest grade of coal; highest purity; crucial to the development of the U.S.; nonfoliated
Graphite
no longer considered coal; but pure carbon; nonfoliated
Shock Metamorphism
This occurs when high speed projectiles called bolides strike Earth's surface; products are called impactites; extremely high pressure
Most metamorphism occurs along ________ plate boundaries
convergent
Contact or Thermal Metamorphism Environments
Environments that result from a rise in temperature when magma invades a host rock; a zone of alteration forms in the rock surrounding the magma
Hydrothermal Metamorphic Environments
An environment mostly along the axis of the mid-ocean ridge system caused when hot ion-rich fluids circulate through fissures and cracks that develop in rock; ZEOLITE FACIES
Structural Geology
the study of the processes responsible for and results of deforming the Earth's crust
deformation
any change in original form and/or size.
3 Types of Stress
compressive
tensional
shear
(look at diagrams in notes)
Strain
response to stress; a change in the shape or size of a rock body
Rocks subjected to stresses greater than their own strength deform by...
fracturing, folding, or warping
Elastic Deformation
the rock returns to its original size and shape when the stress is removed
Brittle Deformation
also called fracture of rupture. ex: pencil
Plastic Deformation
the rock folds or warps and does not return to its original size and shape when the stress is removed. ex: paperclip
Joints
fractures with no movement along the fracture surfaces.
Most occur in roughly parallel groups
Significance (Differential Weathering)
chemical weathering tends to be concentrated along joints because of the increased surface area created
Joints promote chemical weathering by... (3)
1. Decomposition of unstable minerals
2. generation or retention of stable materials
3. physical changes such as the rounding of corners or edges
Faults
fractures with appreciable movement along the fracture surfaces.
*classified based on their direction of movement
Normal Faults
Hanging wall drops relative to footwall; accommodate lengthening or extension of the crust; strong tensional forces; horsts & grabens
Reverse Faults
Hanging wall block moves up relative to the footwall block; accommodate shortening of the crust; strong compressional forces
Thrust Faults
low angle reverse faults (less than 25 degrees)
Strike-slip Faults
dominant displacement is horizontal and parallel to the strike of the fault
Dextral strike-slip faults
opposite side appears to have moved to one's right
Sinistral strike-slip faults
opposite side appears to have moved to one's left
T/F: Strain is the response of a material, such as rock, to applied stress.
True
Folds
during crustal deformation rocks are often bent into a series of wave-like undulations called folds
*most folds result from compressional stresses which shorten and thicken the crust
Anticline Folds
upfolded or arched rock layers
Syncline Folds
downfolded or troughs of rock layers
Anticlines & Synclines can be described as... (4)
symmetrical
asymmetrical
recumbent (fold over on themselves)
plunging (folds that meet the surface at an angle)
Dome Folds
unwarped displacement of rocks; circular or slightly elongated structure; oldest rocks in center with younger rocks on the flanks
Basin Folds
downwarped displacement of rocks; circular or slightly elongated structure; youngest rocks near the center and older rocks on the flanks
Which of the following is NOT a manifestation of brittle deformation?
rock fracture
jointing
faulting
folding
folding
Which of the following is NOT a geologic structure resulting from ductile deformation?
syncline
anticline
thrust fault
dome
thrust fault
Metamorphism
The transformation of one rock into another by temperatures and/or pressures unlike those in which the original rock formed.
Metamorphic rocks can be produced from.. (3 things)
Igneous rocks
Sedimentary rocks
Other metamorphic rocks
Metamorphic rock cannot melt but undergoes changes is... (2)
Viscosity
Crystallography
Viscosity
loss of cohesion between crystals/grains
Crystallography
atomic arrangement within crystals
Agents of Metamorphism (3)
Heat
Pressure
Chemically active fluids
Contact or Thermal metamorphism
A type of metamorphism that results from intrusion of magma into a host rock
Hydrothermal metamorphism
A type of metamorphism that happens as a result of chemical alterations from hot, iron-rich water
Regional metamorphism
A type of metamorphism that occurs during orogenesis; produces the greatest volume of metamorphic rock; usually displays zones of contact and/or hydrothermal metamorphism
Heat (as an agent of metamorphism)
Agent comes from ____ in magma and an increase in temperature with depth due to the geothermal gradient.
Pressure (as an agent of metamorphism)
An agent of metamorphism that can be isotropic or anisotropic.
Isotropic
Confining pressure applies forces equally in a ll directions and increases with depth
Anisotropic
Unequal pressure in different directions; induces differential stresses or shear stresses.
Chemically active fluids (as an agent of metamorphism)
Mainly water with other volatile components; enhances migration of ions; aids in recrystallization of existing minerals
Sources of chemically active fluids (3)
Pore spaces of sedimentary rocks
Fractures in igneous rocks
Hydrated minerals such as clays and micas
The importance of parent rock
most metamorphic rocks have the same chemical composition as the _________________ from which they formed.
Texture
The size, shape, and arrangement of mineral grains
Two types of metamorphic texture
Foliated
Non-foliated
Foliation
Any planar arrangement of mineral grains or structural features within a rock
Examples of foliation (3)
parallel alignment of flattened mineral grains and pebbles
Compositional banding
Rock cleavage
Ways foliation can form (3)
Rotation of platy and/or elongated minerals
Recrystallization of minerals in a preferred orientation
Changing the shape of equidimensional grains into elongated shapes that are aligned or rotated
Foliated Textures
The texture that results from differential stresses
Non-foliated Textures
The texture that results from confining pressure
Types of Foliated Textures (4)
Slaty parting
Schistocity or Schistos
Gniessic banding
Augen
Types of non-foliated textures
Fused Granular Texture (most common)
Prophyroblastic Texture
Eclogitic Texture
Common Metamorphic Rocks in the continuum with increasing pressure & temperature going down.
Sediment
Sedimentary Rock
Foliated metamorphic rocks
____ is formed from sediment.
Clays
_____ is formed from sedimentary rock.
Shale
4 types of foliated metamorphic rocks
Slate
Phyllite
Schist
Gneiss
Slate
A very fine-grained foliated rock with excellent cleavage; generated from shale; platy minerals not large enough to be see with an unaided eye.
Phyllite
Made of small platy minerals; glossy sheen & wavy surfaces; contains fine crystals of muscovite and/or chlorite micas
Schist
Medium to course grained; made of mainly platy minerals (micas)
Gneiss
Contains medium to course-grained grains; banded/warped appearance; high-grade metamorphism; often white or light-colored feldspar with bands of dark ferromagnesian mineras
Fused Granular Texture (4 types)
Quartzite
Argylite/Hornfels
Marble
Anthracite
Quartzite
A nonfoliated rock; formed from quartz-rich sandstone; quartz grains are fused together giving it a feathery/overlapping appearance
Argylite
A nonfoliated rock; formed from a predominantly clay parent rock (shale); tightly fused fine-grained metamorphic rock; so small you can't see
Marble
Coarse; crystalline; parent rock was limestone or dolostone; used as a monument stone; PROBLEM: dissolves with a weak and small amount of acid
Anthracite Coal
formed from plan matter; highest grade of coal; highest purity; crucial to the development of the U.S.; nonfoliated
Graphite
no longer considered coal; but pure carbon; nonfoliated
Shock Metamorphism
This occurs when high speed projectiles called bolides strike Earth's surface; products are called impactites; extremely high pressure
Most metamorphism occurs along ________ plate boundaries
convergent
Contact or Thermal Metamorphism Environments
Environments that result from a rise in temperature when magma invades a host rock; a zone of alteration forms in the rock surrounding the magma
Hydrothermal Metamorphic Environments
An environment mostly along the axis of the mid-ocean ridge system caused when hot ion-rich fluids circulate through fissures and cracks that develop in rock; ZEOLITE FACIES
Structural Geology
the study of the processes responsible for and results of deforming the Earth's crust
deformation
any change in original form and/or size.
3 Types of Stress
compressive
tensional
shear
(look at diagrams in notes)
Strain
response to stress; a change in the shape or size of a rock body
Rocks subjected to stresses greater than their own strength deform by...
fracturing, folding, or warping
Elastic Deformation
the rock returns to its original size and shape when the stress is removed
Brittle Deformation
also called fracture of rupture. ex: pencil
Plastic Deformation
the rock folds or warps and does not return to its original size and shape when the stress is removed. ex: paperclip
Joints
fractures with no movement along the fracture surfaces.
Most occur in roughly parallel groups
Significance (Differential Weathering)
chemical weathering tends to be concentrated along joints because of the increased surface area created
Joints promote chemical weathering by... (3)
1. Decomposition of unstable minerals
2. generation or retention of stable materials
3. physical changes such as the rounding of corners or edges
Faults
fractures with appreciable movement along the fracture surfaces.
*classified based on their direction of movement
Normal Faults
Hanging wall drops relative to footwall; accommodate lengthening or extension of the crust; strong tensional forces; horsts & grabens
Reverse Faults
Hanging wall block moves up relative to the footwall block; accommodate shortening of the crust; strong compressional forces
Thrust Faults
low angle reverse faults (less than 25 degrees)
Strike-slip Faults
dominant displacement is horizontal and parallel to the strike of the fault
Dextral strike-slip faults
opposite side appears to have moved to one's right
Sinistral strike-slip faults
opposite side appears to have moved to one's left
T/F: Strain is the response of a material, such as rock, to applied stress.
TRUE
Folds
during crustal deformation rocks are often bent into a series of wave-like undulations called folds
*most folds result from compressional stresses which shorten and thicken the crust
Anticline Folds
upfolded or arched rock layers
Syncline Folds
downfolded or troughs of rock layers
Anticlines & Synclines can be described as... (4)
symmetrical
asymmetrical
recumbent (fold over on themselves)
plunging (folds that meet the surface at an angle)
Dome Folds
unwarped displacement of rocks; circular or slightly elongated structure; oldest rocks in center with younger rocks on the flanks
Basin Folds
downwarped displacement of rocks; circular or slightly elongated structure; youngest rocks near the center and older rocks on the flanks
Which of the following is NOT a manifestation of brittle deformation?
rock fracture
jointing
faulting
folding
folding
Which of the following is NOT a geologic structure resulting from ductile deformation?
syncline
anticline
thrust fault
dome
thrust fault