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GLE Reviews > Earth Mat Flashcards - Ch 10 > Flashcards

Earth Mat Flashcards - Ch 10

1
Q

are suites of rocks that form in response to similar geological conditions.

A

Petrotectonic associations

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2
Q

% magma generated at moden divergent, convergent, and hotspots

A

62, 26, and 12%

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3
Q

Layer 3 of the oceanic crust contains

A

Istoropic gabbro (upper)
Cumulate gabbro (mid)
Cumulate peridotite (lower)

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4
Q

are tholeiites with low SiO2, low potassium, high MgO, Al2O3 and compatible elements concentrations

A

MORB

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5
Q

what does depleted source mean in the context of igneous petrology

A

mantle lherzolite undergone previous melt cycles that has largely removed imcompatible elements

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6
Q

N-MORB vs E-MORB

A

N-MORB depleted in imcompatible elements (LREE, HFS, LIL)
E-MORB has La/Sm >1 ratio,

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7
Q

What does the presence of E-MORB represent

A

small degrees of partial melting (10-15~)
tapping aa deep mantle source
enriched from magmaa mixing, assimilation, or partial melts from subducted oceanic lithosphere

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8
Q

Basats where Al2O3 concentrations exceed 16%
Low K2O

A

High Aluminum Basalts or
ARC THOLEIITES

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9
Q

Describe the rocks produced by oceanic ridges

A

High alumina basalts
Higher TiO2 (>13%) concentration in andesitic and rhyolitic basalts

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10
Q

thinner ocean lithosphere in the overlying plate generally produces

A

metaluminous, mafi c to intermediate rocks

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11
Q

Thicker continental lithosphere overlying the subduction zones commonly yields

A

peraluminous, potassic, intermediate to silicic rocks.

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12
Q

Phanerozoic convergent margins are dominated by what magma series

A

Calc - alkaline

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13
Q

Signature calc-alkaline association of convegent margin

A

Basalt Andesite Dacite and Rhyolite (BADR)

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14
Q

How does Calc-Alkaline basalts differ from tholeiites

A

higher alkali, no Fe enrichment

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15
Q

SiO2 range of Andesites

A

> 52-63%

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16
Q

Common in youthful Island arc systems
>52-57% SiO2

A

Basaltic Andesite

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17
Q

Common in mature Island arc systems
>57-63% SiO2

A

Silicic Andesites

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18
Q

Conditions for voluminous andesite production

A

> 25° subduction angles
25 km continental crust anatexis
70-200 km deep subduction

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19
Q

are quartz – phyric volcanic rocks, intermediate between andesite and rhyolite

A

Dacite

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20
Q

SiO2 range of Dacite

A

63-68% (most dacites)
extends to 77%^ in TAS

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21
Q

Plutonic equivalent of dacites

A

granodiorites

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22
Q

common dacite phenocryst

A

Olioclase to labradorite
Sanidine

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23
Q

are generally composed of ∼ 66 – 69% SiO 2 , although the lower TAS limit begins at 57% SiO

A

Trachyandesites

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24
Q

Trachyandesites commonly contain phenocrysts of ___________plagioclase feldspar amidst a groundmass of ____________

A

andesine to oligoclase
orthoclase and augite.

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25
Q

Variations of Arc Rocks in terms of K2O concentratio

A

High - Calc Alkaline to Shoshonite (>40 km thick overlying slab)
Mid - Calc Alkaline (20-40 km)
Low - Tholeiite (0 - 20km)

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26
Q

________ which represent the plutonic equivalent of dacites and rhyodacites, contain > 20% quartz and more plagioclase than potassium feldspar

A

Granodiorites

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27
Q

Island arc granodiorites are generally

A

metaluminous, containing hornblende, biotite and minor amounts of muscovite.

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28
Q

Plagiogranite types

A

Tonalites and Trondhkemites

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29
Q

In Island arc pluton first described from Monte Adamello near Tonale in the eastern Alps, contain calcium plagioclase and quartz with minor amounts of potassium feldspar, biotite and hornblende.

A

Tonalites

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30
Q

are granodioritic rocks in which sodium plagioclase represents half to two - thirds of the total feldspar component.
depleted Bt and Pl

A

Trondhjemites

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31
Q

Low poratssium arc tholeiites occur on the

A

ocean side of the volcanic arc

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32
Q

How are Is. Arc Tholeiite basalts distinguised from MORB

A

greater concentrations of potassium and other LIL elements and lower concentrations of HFS elements

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33
Q

are high magnesium (MgO/MgO + total FeO > 0.7) intermediate volcanic rocks that contain a SiO 2 - saturated (52 – 68% SiO 2 ) groundmass.

A

Boninites

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34
Q

Other properties of Boninites include:
- Opx phenocrysts (with a lack of plagioclase)
- HREE, HFS Depletion
- Enrichment in Xr, Ni, Zn, Ba, Sr
- Magma derived found trench proximal
What does this imply?

A

boninites are aproduct of subduction related melting in forearc of youthful is. arc sys.

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35
Q

are silica - saturated ( > 56% SiO 2 ) rocks with high Sr/Y and La/Yb ratios (LREE enriched relative to HREE) and low HFS, (such as Nb and Ta) concentrations
Are also the volcanic equivalent of TTGs

A

Adakites

36
Q

formational conditions of adakite

A

slab melting of eclogite / garnet amphibolte from desecding ocean lithosphere
continent-continent collision sites: shallow subduction

37
Q

the TTG association is called

A

Tonalite, Trondhjemite, Granodiorite associateions

38
Q

this magma assosication is generated by fractional crystallization of basaltic magma derived by partial melting of overlying mantle peridotite fluxed by fluids from the subducting slab

A

Calc - alkaline

39
Q

TTG are associated with what environment

A

Achean (more dominant) to Recent Subduction zones

40
Q

An opx bearing suite of rocks of generally granitic composition, occurs with TTG

A

Charnockites

41
Q

How are archean subductions described

A

Higher geothermal gradients
shallow subduction and melting of ocean lithosphere
minimal input from overlying lithosphere wedge
abundance of tonalite plutons and adakite volcanics

42
Q

These basalts are enriched with H20, Alkalis and LIL elements
REE 5-20x that of chrondrites
Relative enrichment in volatile elements, Th and LREE (subduction related fluid in magma genesis)
found in Back arc basins

A

Back Arc Basin Basalts (BAB)

43
Q

Why does BAB produce a wide array of rock types

A

Mutiple processes
- partial melt of mantle perodotite (MORBS)
- Hydrated mantle wedge, recycled subducted lithosphere, subducted marine sediment sources (Calc-Alkaline)
- Adiabatic melt of mantle peridotites at BAB ridges

44
Q

Imagine the TiO2, MnO x 10, P2o5 x 10 ternary diagram

A

Ti02 at top, MnO at left, P2O5 at right
TiO2 rich : MORB (L), OIT (R)
MnO : CAB (L + Bot), IAT (L + Up)
P2O5 : OIA (R)
Search sa net ang ternary

45
Q

Imagine the Ti/100, Zr, Y x 3 ternary diagram

A

Ti/100 top, Zr left, Y x 3 right
Ti/100 : WBP (L), IAT (R)
Zr : CAB
Mid : MORB IAT

46
Q

are dark - colored, potassium - rich trachyandesites, commonly containing olivine and augite phenocrysts with a groundmass of labradorite plagioclase, alkali feldspar, olivine, augite and leucite.

A

Shoshonites

47
Q

Petrotectonic characteristics of Shoshonites

A

late stage ocean-continent subduction
occurs in thickened lithosphere farthest from trench region, in continent-continent collisions, and some back arc basins

48
Q

Conditions for the formation of rhyolites, rhyodacites and shoshonite and granitic plutons

A

-flat subduction (<25°)
-thick continental lithospehre (>25)

49
Q

the kind of basalts seen in continent-continent collisions

A

alkaline basalts, from upwelling mantle melts

50
Q

Strictly speaking, the term “ granite ” is restricted to plutonic rocks containing

A

20 – 60% quartz and
35 – 90% alkali to plagioclase feldspars

51
Q

Orogenic granites
Anorogenic granites

A

M, I, S types
A type

52
Q

mantle derived parental magmas (87Sr/86Sr < 0.704)
associated with calc-alkaline tonalites, qtz diorite and gabbroics
develop in Is. Arc settings

What granite

A

M type

53
Q

melting of igneous protolith from subduction (slab or wedge)
Na2O and Ca2O enrichment, Al2O3 depletion
Mantle Source (87Sr/86Sr < 0.704)

What granite

A

I type

54
Q

Melting of sedimentary crustal rocks in collision zones
Na2O depletion, Al2O3 enrichment (peraluminous)
Ealier sedimentary cycle (87Sr/86Sr < 0.704)
Also known as Two-Mica Granites, Hb absent

What granite

A

S-Type

55
Q

Anorogenic; does not involve subduction and collision
Alkali and LIL enriched, depleted in refractory elements
peralakline
low water contents

A

A type

56
Q

Mineralizations associated with granites

A

Au-Cu mineralization : M type
Cu, Mo, W deposits : I type
Sn deposits : S Type

57
Q

are fault - bounded, deformed rock sequences that mark the site of present or former convergent margins

A

Alpine orogenic complexes

58
Q

constitute one type of Alpine deposit in which the oceanic or backarc basin lithosphere or volcanic arc basement rocks are preserved in orogenic belts

A

Ophiolites

59
Q

A trinity associated wuth ophiolites, consist of pelagic chert, serpentinite, and spilites

A

Steinmann trinity

60
Q

these ophiolites develop due to extensional tectonics that result in backarc spreading or forearc spreading producing oceanic lithosphere.

A

SSZ Ophiolites

61
Q

consist of concentrically layered (zoned) plutons formed in convergent margin settings.

A

Alaska - type intrusions

62
Q

Zones in an alaska type intrusio

A

Dunite core, Pyroxenite shell, surrounded by massive gabbro, occasional granitic zones in its perimeter

63
Q

Alaska - type intrusions are economically important as sources of metals, particularly

A

PGE

64
Q

Intraplate magmatism produces a wide range of igneous rock types including:

A

-Tholeiitic to alkalic basalt and related gabbros of hotspots and LIP.
-Siliceous anorogenic granite and rhyolite.
-Silica - undersaturated rocks.
-Basic – ultrabasic suites including komatiites and kimberlites.
-Carbonatites.

65
Q

greatest manifestation of intraplate magmatism

A

LIPs (>10^6 km^3)

66
Q

What kind of LIP is Yellowstone

A

Silicic LIP (SLIP)

67
Q

How are OIB different from MORB

A

moaare alkalic, less depleted
from partial melts of deeper and undepleted mantle source

68
Q

Hypothesis proposed for OIB chemistry

A
  • Small degrees of melting of a primitive mantle source.
  • Melting of a mantle source enriched in alkali elements.
  • Incorporation of subducted oceanic crust in the source region.
  • Entrainment of subducted sedimentary rocks in the source region
69
Q

Nepheline normartive OIB magmas are derived from

A

Parial melting of gar px,
gar px came from MORB and mantle peridotite mixing

70
Q

Fractionization sequence at OIB

A

Increasing SiO2 (x) and Alkalis (y)
-Basalts -> Hawaiites -> Mugeraites -> Benmorites -> Trachyte -> Phonolites (Silica undersat) or Rhyolites (Silica Oversat)

71
Q

Largest flood basalt events

A

Siberian Traps : Permo-Triassic
CAMP : Triassic-E. Jurrasic
Deccan Trap : Cret-Ternary
also corresponds with the largest extinctions in history

72
Q

Continental rifts produce a wide array of rocks that include

A

alkalic basalt, alkaline and silicic rocks

73
Q

The widespread occurrence of basalt and rhyolite without significant andesite is referred to as

A

bimodal volcanism

74
Q

Bimodal Volcanim occurs in

A

Continental rifts and hotspots

75
Q

are anorogenic bodies injected into stable continental cratons at moderate depths

A

Layered basic – ultrabasic intrusions

76
Q

largest layed intrusio

A

Stillwater complex, Montana
Bushveld Complex, S. Africa
Skaergaard Intrusion, Greenland

77
Q

are ultrabasic volcanic rocks found almost exclusively in Archean (>2.5 Ga) greenstone belts

A

Komatiites

78
Q

consists of needle - like, acicular olivine, pyroxene (augite and/or pigeonite) and chromite phenocrysts in a glassy groundmass

A

Spinifex texture

79
Q

Spinifex texture can be found on

A

Upper parts of komatiite flows; chilled margins of silla and dikes

80
Q

Only known phanerozoic (younger) komatiites

A

Gorgona Is., Colombia

81
Q

Komatiite origin

A

Melting in hydrated mantle wedge
deep mantle plume hotspot leading to large partial melting
Gar Peridotite partial melting (10-30%) at 8-10 Gpa

82
Q

are brecciated, magnesium - rich, ultrabasic rocks that rapidly rise to Earth ’ s surface via cylindrical diatremes from deep within the mantle.

A

Kimberlites

83
Q

important CO2 energy sources propelling kimberlites

A

Carbonate minerals

84
Q

are shallow intrusive to volcanic rocks that contain > 20% CO3 minerals

A

Carbonatite

85
Q

are magnesium - rich, volatle - rich, porphyritic rocks containing mafic phenocrysts such as biotite, phlogopite, amphibole, clinopyroxene and melilite.

A

Lamprophyres

86
Q

are potassium - rich, peralkaline rocks containing minerals such as leucite,sanidine, phlogopite, richterite, diopside and olivine.

A

Lamproites

87
Q

this texture refers to sodium plagioclase overgrowths on pre -existing orthoclase crystals

A

Rapakivi

GLE Reviews (26 decks)

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