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GLY 205 > Igneous Rocks > Flashcards

Igneous Rocks Flashcards

1
Q

IGNEOUS ROCKS formed by?

A

Solidification of magma

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2
Q

slow cooling = ________ ?

rapid cooling = ________ ?

A 
slow   =   CRYSTALLIZATION
rapid   =   QUENCHING
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3
Q

Classified by? ( 2 )

A

1 ) COMPOSITION (chemistry)

2 ) TEXTURE (crystal size/shape)

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4
Q

ULTRAMAFIC

  • SiO2 content?
  • Major Minerals?
  • Rock Types (P/A) ?
A
  • <45% SiO2
  • Olivine, Pyroxene (pos amphibole, garnet)
  • Peridotite (P)
  • Komatite (A)
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5
Q

MAFIC

  • SiO2 content?
  • Major Minerals?
  • Rock Types (P/A) ?
A
  • 45-52% SiO2
  • Pyroxene, Olivine, Plagioclase (pos amphibole, biotite)
  • Gabbro (P)
  • Basalt (A)
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6
Q

INTERMEDIATE

  • SiO2 content?
  • Major Minerals?
  • Rock Types (P/A) ?
A
  • 52-66% SiO2
  • Plagioclase, Amphibole (pos biotite, potassium feldspar)
  • Diorite (P)
  • Andesite (A)
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7
Q

FELSIC

  • SiO2 content?
  • Major Minerals?
  • Rock Types (P/A) ?
A
  • > 66% SiO2
  • Potassium feldspar, Quartz (pos biotite, amphibole)
  • Granite, Granodiorite (P)
  • Rhyolite, Dacite (A)
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8
Q

T A S Diagram

A
  • Total Alkali vs. Silica content evolution
  • used to group volcanic rock types
  • composition dependent
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9
Q

Dark minerals dominate?

A

Melanocratic

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10
Q

Light minerals dominate?

A

Leucocratic

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11
Q

2 Examples of MISLEADING Color

A

1) Obsidian >66% SiO2 but black

2) Dunite >90% Olivine but pale green

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12
Q

Fine-grained (<1mm) ?

A

Aphanitic

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13
Q

Coarse-grained (1-30mm) ?

A

Phaneritic

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14
Q

VERY Coarse-grained (>30mm) ?

A

Pegmatitic

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15
Q

Mix of large and small grains?

A

Porphyritic

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16
Q

No crystals present?

A

Glassy (vitreous)

17
Q

Texture created by trapped gas bubbles

*More common in FELSIC (more viscous, trap gas more easily)

A

Vesicular

18
Q

Property of rocks that indicates ability of fluids/gases to flow through rock

A

PERMEABILITY

19
Q

Rocks that are formed in the Earth’s crust

A

Intrusive / Plutonic

20
Q

Rocks that are formed at the Earth’s surface

A

Extrusive / Volcanic

21
Q

No constraints of on space - clean crystal faces develop

A

EUHEDRAL

22
Q

Constraints on space - poor/no crystal faces develop

A

ANHEDRAL

23
Q

Mix of some crystal faces and no crystal faces

A

SUBHEDRAL

24
Q

Rocks that plot near P on QAPF (type + 3 EX)

A

MAFIC PLUTONIC ROCKS

  • Anorthosite
  • Gabbro
  • Diorite
25
Q

Texture controlled by interplay of ? (2)

A
  • Nucleation rates (how quickly new seed crystals are formed from melt)
  • Crystal growth rates (how quickly atoms build on a crystal lattice)
26
Q

Factors in texture controls ? (3)

A
  • viscosity
  • ion availability
  • volatile composition (H2O, CO2, SO2 - volatiles prevent SiO2 bonding = keeps viscosity low)
27
Q

Si-deficient feldspar-like minerals ?

A

Quartz + Feldspathoids

28
Q

Temperature-depth relationship of the Earth

A 
the GEOTHERM
(melting points higher because of higher pressure)
29
Q

How are MELTS formed? (3)

A
  • Temperature increase
  • Decompression
  • Volatile addition (H2O, CO2)
30
Q

________ : As temperature increases in a rock ______ minerals will break down first

A

PARTIAL MELTING; SILICA-RICH

SiO2, K2O, Na2O

31
Q

________ : As temperature decreases in a melt, ______ minerals crystallize first and fall out of solution

A

FRACTIONAL CRYSTALLIZATION;

MAFIC

32
Q

Edges of the magma chamber cool faster and crystallize first, leaving hot center

A

MARGINAL ACCRETION

33
Q

Crystal settling and floating

A

Gravitational Separation (differentiates magma chamber w/ layering)

34
Q

When crystals grow on wall of intrusion due to density currents

A

Convective Fractionation

35
Q

Melting of rocks around an intrusion, mixing with magma within the intrusion

A

Assimilation

GLY 205 (2 decks)

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