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Metamorphic Rock Flashcards

1
Q

metamorphic change (3)

A

Neo-crystallization
Foliation
Re-crystallization

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2
Q

Plastic deformation

A

mineral grains soften and deform
increased temperature and pressure
dont break, behave plastically

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3
Q

Agents of metamorphism (4)

A

1) Heat (T)
2) Pressure (P)
3) Compression and shear
4) Hot water

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4
Q

Sources of heat (3)

A

1) Geothermal gradient
2) Magmatic intrusions
3) Tectonic compression

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5
Q

Where does metamorphism occur?

A

2-12 Kbars = 6.5-40km

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6
Q

Kinds of differential stress (2)

A

Normal stress

Shear stress

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7
Q

Normal stress

A

operates perpendicular to surface

Tension-compression

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8
Q

Shear stress

A

moves one part of the material sideways

causes material to be smeared out

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9
Q

Shape changes due to differential stress (2)

A

Equant: equal in all dimensions
Inequant: not equal in all dimensions

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10
Q

Do metamorphic rocks prefer equant of inequant dimensions

A

Inequant dimensions

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11
Q

How does preferred mineral orientation develop?

A
  • Shear rotation and flattening
  • Shear flattens grains in a manner similar to compression
  • Shear rotates grains into alignment
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12
Q

Hydrothermal alteration is called _______

A

Metasomatism

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13
Q

Major divisions of Metamorphic rocks (2)

A

1) foliated

2) non-foliated

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14
Q

Foliated metamorphic rocks

A
  • through going planar fabric
  • crystallized with differential stress
  • planty minerals
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15
Q

Non-foliated metamorphic rocks

A
  • no planar fabric
  • crystalized without differential stress
  • equant minerals only
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16
Q

Foliation

A
  • Parallel planar surfaces
  • Streaked or striped appearance
  • Foliated rocks often break along foliation planes
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17
Q

Slate

A

Fine grained

low grade metamorphic shale

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18
Q

Schist

A

Fine to course rock with larger Mica’s
medium to high grade metamorphism
shistosity (type of foliation)

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19
Q

Large non-mica minerals

A

porphyroblasts

20
Q

Gneiss

A

distinct banded foliation
light bands: Feldspar/quartz
dark bands: biotite/amphibole

21
Q

compositional banding development (3)

A

1) Original layering in the protolith
2) Extensive high T shearing
3) Metamorphic differentiation

22
Q

Migmatite

A

Partially melted gneiss

feature of igneous and metamorphic rock

23
Q

Hornfels

A

alteration by heating (contact metamorphism)

baked contact by igneous rock

24
Q

Amphibolite

A

protolith of gabbro or basalt
High is Mg and Fe
foliation under differential stress

25
Quartzite
pure quartz in composition formed by alteration in quartz sandstone conchoidal fractures
26
Marble
crystalline calcite or dolomite | limestone or dolostone protolith
27
Broad compositional classes (4)
1) Pelitic 2) Mafic 3) Calcareous 4) Quartzo
28
Pelitic class
derived from shale protolith | Al rich so form Micas
29
Mafic
basalt or gabbro protolith
30
Calcareous
carbonate protolith
31
Quartzo-feldspathic
granite protolith
32
Metamorphic grade is a measure of ______
Intensity
33
Low metamorphic grade | High metamorphic grade
Low T and P | High T and/or P
34
Prograde metamoprphism
Metamorphism with increasing T and P | burial process
35
Retrograde metamorphism
Metamorphism with decreasing T and P Requires addition of H2O Rocks move towards surface
36
Metamorphic Facies
Grew in association with other rock in the same P and T Derived from the same: 1) protolith 2) P and T conditions
37
Types of Metamorphic environments (7)
1) Thermal 2) Burial 3) Dynamic 4) Regional 5) Hydrothermal 6) Subduction 7) Shock
38
Thermal metamorphism
- Thermal baked contact - Grades of alteration form aureoles around the pluton - contact between magma and other rock
39
Burial metamorphism
As sediments are buried in sedimentary basin: T increases due to geothermal gradient; P increase due to overburden ~8-15Km deep
40
Dynamic metamorphism
breakage of rock due to shear forces at fault zone Shallow (<15km): Fault Breccia Deep (<15km): Fault Mylonite
41
Regional metamorphism
collisions form huge "mobile belts" Compression adds to mountain ranges creates foliated rocks
42
Hydrothermal metamorphism
hot water deformation | mid-ocean ridge magma
43
Subduction metamorphism
bluesheist facies trenches and accretionary prisms High P - Low T - Glaucophale: Blue amphibole
44
Shock Metamorphism
asteroid compressional shockwave heat vapourizes large amount of ground - Coesite, schisovite
45
Exhumation
how rocks return to the surface 1) uplift 2) extensional collapse 3) erosional unrooting
46
Where are most metamorphic rocks found?
continental interiors

Geology (5 decks)

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