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

Test #1 Flashcards

(67 cards)

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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
Tabular vs. non-tabular
Tabular plutons are "table"-like, cut across (think 3D)
26
Concordant vs. discordant plutons
* Concordant runs parallel to country rock * Discordant cuts across country rock
27
Dikes vs. Sills
28
Xenolith
Fragment of country rock that is broken off and enclosed within magma chamber
29
Laccolith
Highly viscous lava, does not spread out like a sill
30
Lopolith
Dense mafic magma, causes basin floor to sag
31
Batholith
* Non-tabular * Viscous lava * Instrusive * Exposed areal extent \> 100 km2
32
Stock
* Non-tabular * Viscous lava * Instrusive * Exposed areal extent \< 100 km2
33
Epizone
Shallow level Country rocks \< 300°C
34
Mesozone
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
Catazone
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
Diapir
37
How does magma displace solid country rock? (4)
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
Composition of ultramafic magma
\<45% SiO2 Very rich in Mg, Fe
39
Composition of mafic magma
SiO2 content of 45-52% Rich in Mg, Ca, Fe
40
Composition of intermediate magma
SiO2 content of 52-65% Na/Ca composition
41
Composition of felsic magma
SiO2 content of 65-75% Rich in Al, Na, K
42
Viscosity
* Resistance to flow * Increases w/Si-O & Al-O bonds * Felsic--generally most viscous
43
Volatiles
(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
Shield Volcano
Very large landforms, caused by low viscosity (mafic) magma
45
Cinder cone
* De-gassed (therefore more dense) magma * Often form on other types of volcanoes
46
Composite Volcano
* Tall * Built up layers * Often thick felsic magma
47
Lava dome
"Bubble"-shaped extrusion formed by highly viscous magma
48
Flood basalt
Plateau formed by basaltic eruption of very low viscosity lava
49
Plinian eruption
Pyroclastic eruption that produces very high ash plume
50
Pyroclastic flow
* Cloud of pyroclastic material and gases * Extremely hot (400-800°C) * Can move 50-200km/hr
51
Pyroclastic Deposit
* Poorly sorted * Ash mixed with pumice & lithic fragments
52
Pyroclastic Textures
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
Caldera
Large pit formed by collapse after eruption
54
Phreatic eruption
Hot magma comes in contact with surface/groundwater; produces steam
55
Maar
Crater formed by deep phreatic explosion
56
Tuff ring
Basaltic magma reacts with shallow ground/surface water
57
Tuff cone
Smaller & steeper; less violent phreatic eruption
58
System
Portion of the universe that you wish to study **Natural systems tend toward states of minimum energy.**
59
Energy States
Unstable Stable: at rest in lowest energy state Metastable: at rest in temporary low-energy "perch"
60
Gibbs Free Energy
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
Phase
Seperable portion of a system (ex: different minerals in a rock)
62
Reaction
Change in the nature or phase of a system **reactants = products** *Must be balanced!*
63
ΔG
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
Formula for determining G for P & T different from reference state
GT2P2= GT1P1 + V (P2 - P1) - S (T2 - T1)
65
Extensive Variables
Depend on quantity 1. Mass 2. Volume 3. Free energy
66
Intensive Variables
Do not depend on size 1. Pressure 2. Temperature 3. Density 4. Molar volume
67
Augite
(Ca,Mg,Fe,Na)(Mg,Fe,Al)(Si,Al)2O6

Igneous & Metamorphic Petrology Spring 2013 (2 decks)

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