Lecture 9// Metamorphic Rock Flashcards

Chapter 9

1
Q

Metamorphism (5)

A

Changes to the mineralogy and texture of pre-existing rock due to:

  • increased pressure
  • increased temperature
  • increased chemically active fluids

Solid-state transformations (no or very little melting involved).

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2
Q

Parent rock / Protolith (2)

A
The original (pre-existing) rock type before it underwent metamorphism.
-ex. Shale (or mudstone) is a common parent rock of slate.
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3
Q

Foliation (2)

A

Some metamorphic rocks show a preferred orientation to the grains (layering or alignment) as a response to a directed stress.
-ex. Granite to Gneiss

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4
Q

Regional Metamorphism (1)

A

Directed stress occurs due to compressive forces acting within large regions at and adjacent to convergent plate margins.

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5
Q

Metamorphic Grade (5)

A

The grade reflects the severity of the metamorphic conditions, increasing grain size & metamorphic grade:

  • Lowest: Slate
  • Phyllite
  • Schist
  • Highest: Gneiss
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6
Q

Slate (3)

A
  • very fine grained & dull
  • slaty cleavage (breaks into very flat layers)
  • clay minerals, chlorite muscovite
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7
Q

Phyllite (3)

A
  • fine-grained
  • phyllitic texture (glossy metallic shine, commonly wavy)
  • chloride, muscovite
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8
Q

Schist (3)

A
  • medium to coarse grained
  • commonly some grains are much larger (porphyroblasts)
  • schistose texture (scaly)
  • muscovite, biotite, kyanite and others
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9
Q

Gneiss (3)

A
  • medium to coarse grained
  • gneissic texture (bands of light and dark minerals)
  • feldspar, quartz, muscovite, biotite. Fe and Mg
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10
Q

Contact Metamorphism (1)

A

Nonfoliated metamorphic rocks are common where there is only lithostatic stress in addition to heat from magma intrusions.

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11
Q

Quartzite (3)

A
  • medium to coarse grained
  • visually can look like marble, but is much harder (scratches glass)
  • sandstone parent rock
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12
Q

Marble (4)

A
  • medium to coarse grained
  • soft
  • reacts easily with acid if it is calcite, slow reaction if dolomite
  • limestone or dolostone parent rock
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13
Q

Hornfels (2)

A
  • fine grained, dark

- shale/mudstone parent rock

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14
Q

Soapstone (4)

A
  • fine or medium grained
  • soft, soapy feel
  • Peridotite parent rock
  • composed primarily of talc, with varying amounts of chlorite, mica amphiboles, carbonates, and other minerals
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