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Igneous & Metamorphic Petrology Spring 2013 > Test #1 > Flashcards

Test #1 Flashcards

1
Q

Quartz

A

SiO2

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2
Q

Muscovite

A

KAl2(AlSi3O10)(OH)2

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3
Q

Orthoclase

(K-feldspar)

A

KAlSi3O8

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4
Q

Augite

A

(Ca,Mg,Fe,Na)(Mg,Fe,Al)(Si,Al)2O6

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5
Q

Biotite

A

K(Mg,Fe)3(AlSi3O10)(OH)2

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6
Q

Olivine

A

(Mg,Fe,Mn)SiO4

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7
Q

In what tectonic environments is magma formed? (7)

A
  1. Mid-oceanic ridges
  2. Intracontinental rifts
  3. Island arcs (convergent)
  4. Active continental margins
  5. Back arc basins (Japan)
  6. Ocean island basalts (hot spots)
  7. Miscellaneous oddities
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8
Q

How does the geothermal gradient vary by location?

A

Tectonically stable: <25°C/km

Oceanic trenches: 5-10°C/km

Mid-oceanic ridges & volcanically active areas:

_>_50°C/km

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9
Q

What is the geothermal gradient?

A

Temperature decreases with depth

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10
Q

How are C° and K related?

A

K=C°+273

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11
Q

How is heat transferred within the solid Earth? (3)

A
  1. conduction – transfer by molecular vibration
  2. convection – buoyancy-driven exchange of heat
  3. advection – passive heat transfer by motion of rock
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12
Q

What are the sources of heat within the Earth? (3)

A
  1. Residual heat from early accretion
  2. Crystallization of inner core
  3. Radioactive decay of U, Th, K, etc. (30-50% of heat reaching the surface comes from radioactive decay)
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13
Q

Types of pressure (4)

A
  1. Lithostatic – by overlying rocks; same in all directions; does not deform rocks
  2. Deviatoric – different pressures in different directions
  3. Hydrostatic – exerted by a column of water
  4. Fluid – exerted by film of fluid in pore spaces
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14
Q

Different units of pressure

A

SI unit: Pascal

1 bar = 0.987 atm = 14.5 psi

1 kbar = 1000 bars

1 bar = 105 Pa

1 kilobar = 0.1 GPa

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15
Q

How are pressure and depth related?

A

P = ϱ g h

P = pressure

ϱ (rho) = density

h = height

g = gravity

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16
Q

Characteristcs of the core

A
  • Fe-Ni metallic alloy
  • Outer core is liquid
  • Inner core is solid
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17
Q

Characteristics of continental crust

A
  • Felsic
  • Thick, light (~35km avg. thickness)
  • Highly variable composition
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18
Q

Characteristics of the mantle

A
  • Ultramafic

Low velocity layer: 60-220 km; seismic waves slow down

410 km: olivine condenses to spinel structure

660 km: spinel structure condenses to perovskite structer

Lower mantle: gradual velocity increase

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19
Q

General characteristics of oceanic crust

A
  • Mafic
  • Dense & thin (<10 km thick)
  • Relatively uniform
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20
Q

Plagioclase feldspar

A

Albite: NaAlSi3O8

Anorthite: CaAl2Si2O8

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21
Q

Bowen’s Reaction Series

A
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22
Q

Feldspar ternary diagram

A
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23
Q

Pyroxene quadrilateral

A
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24
Q

Pluton vs. Country Rock

A
  • Pluton is intrusive
  • Country rock is rock that was originally there
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25
Q

Tabular vs. non-tabular

A

Tabular plutons are “table”-like, cut across (think 3D)

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26
Q

Concordant vs. discordant plutons

A
  • Concordant runs parallel to country rock
  • Discordant cuts across country rock
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27
Q

Dikes vs. Sills

28
Q

Xenolith

A

Fragment of country rock that is broken off and enclosed within magma chamber

29
Q

Laccolith

A

Highly viscous lava, does not spread out like a sill

30
Q

Lopolith

A

Dense mafic magma, causes basin floor to sag

31
Q

Batholith

A
  • Non-tabular
  • Viscous lava
  • Instrusive
  • Exposed areal extent > 100 km2
32
Q

Stock

A
  • Non-tabular
  • Viscous lava
  • Instrusive
  • Exposed areal extent < 100 km2
33
Q

Epizone

A

Shallow level

Country rocks < 300°C

34
Q

Mesozone

A

5-10 km

Country rocks 300-500°C

Country rocks are somewhat ductile at this depth; plutons may be syn- or post-tectonic; foliation may occur in plutons

35
Q

Catazone

A

Deep, <10 km

Country rocks 450-600°C or higher

Catazonal plutons form easily (often concordant), ductile country rock–partial melting of country rock can occur

36
Q

Diapir

37
Q

How does magma displace solid country rock? (4)

A
  1. Doming: upward folding or faulting of overlying strata by magmatic pressure
  2. Wall-rock assimilaton: magma “melts” its way up
  3. Stoping: Brittle country rocks break off and fall into magma (xenoliths may be visible)
  4. Exploitation of shallow pre-existing open fractures
38
Q

Composition of ultramafic magma

A

<45% SiO2

Very rich in Mg, Fe

39
Q

Composition of mafic magma

A

SiO2 content of 45-52%

Rich in Mg, Ca, Fe

40
Q

Composition of intermediate magma

A

SiO2 content of 52-65%

Na/Ca composition

41
Q

Composition of felsic magma

A

SiO2 content of 65-75%

Rich in Al, Na, K

42
Q

Viscosity

A
  • Resistance to flow
  • Increases w/Si-O & Al-O bonds
  • Felsic–generally most viscous
43
Q

Volatiles

A

(volatile components of magma)

H20, CO2

Volatiles can break down polymers & reduce viscosity

Mafic magmas: 0.5-1% volatiles

Felsic magmas: up to 5% volatiles

44
Q

Shield Volcano

A

Very large landforms, caused by low viscosity (mafic) magma

45
Q

Cinder cone

A
  • De-gassed (therefore more dense) magma
  • Often form on other types of volcanoes
46
Q

Composite Volcano

A
  • Tall
  • Built up layers
  • Often thick felsic magma
47
Q

Lava dome

A

“Bubble”-shaped extrusion formed by highly viscous magma

48
Q

Flood basalt

A

Plateau formed by basaltic eruption of very low viscosity lava

49
Q

Plinian eruption

A

Pyroclastic eruption that produces very high ash plume

50
Q

Pyroclastic flow

A
  • Cloud of pyroclastic material and gases
  • Extremely hot (400-800°C)
  • Can move 50-200km/hr
51
Q

Pyroclastic Deposit

A
  • Poorly sorted
  • Ash mixed with pumice & lithic fragments
52
Q

Pyroclastic Textures

A

Pyroclasts/tephra: ash, lapilli, blocks, bombs

Tuff: pyroclastic rock consisting of glass shards, mineral grains, and rock fragments

Ash: pulverized rock & glass, glass shards

53
Q

Caldera

A

Large pit formed by collapse after eruption

54
Q

Phreatic eruption

A

Hot magma comes in contact with surface/groundwater; produces steam

55
Q

Maar

A

Crater formed by deep phreatic explosion

56
Q

Tuff ring

A

Basaltic magma reacts with shallow ground/surface water

57
Q

Tuff cone

A

Smaller & steeper; less violent phreatic eruption

58
Q

System

A

Portion of the universe that you wish to study

Natural systems tend toward states of minimum energy.

59
Q

Energy States

A

Unstable

Stable: at rest in lowest energy state

Metastable: at rest in temporary low-energy “perch”

60
Q

Gibbs Free Energy

A

A measure of chemical energy

G = H - T S

G = Gibbs Free Energy

H = Enthalpy (heat content)

T = Temperature in K

S = Entropy (degree of randomness in atomic arrangement)

61
Q

Phase

A

Seperable portion of a system (ex: different minerals in a rock)

62
Q

Reaction

A

Change in the nature or phase of a system

reactants = products

Must be balanced!

63
Q

ΔG

A

If ΔG is negative, products are stable

If ΔG is positive, reactants are more stable

If ΔG is zero, the system is at equilibrium

64
Q

Formula for determining G for P & T different from reference state

A

GT2P2= GT1P1 + V (P2 - P1) - S (T2 - T1)

65
Q

Extensive Variables

A

Depend on quantity

  1. Mass
  2. Volume
  3. Free energy
66
Q

Intensive Variables

A

Do not depend on size

  1. Pressure
  2. Temperature
  3. Density
  4. Molar volume
67
Q

Augite

A

(Ca,Mg,Fe,Na)(Mg,Fe,Al)(Si,Al)2O6

Igneous & Metamorphic Petrology Spring 2013 (2 decks)

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