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GLE Reviews > Earth Mat Flashcards - Ch 8 > Flashcards

Earth Mat Flashcards - Ch 8

1
Q

Solidify to produce igneous rocks in Earth’s crust are initially formed by a process called ___, which refers to the partial melting of a source rock.

A

anatexis

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2
Q

Anatexis produces:

A

A liquid melt fraction enriched in lower temperature constituents.
A residual rock component enriched in higher temperature, refractory elements.

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3
Q

In the simplest approach, rock melting within Earth’s interior is modeled as two idealized end-member processes:

A

equilibrium melting and disequilibrium (fractional) melting.

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4
Q

occurs in a closed system where chemicals are neither added nor removed from the plutonic environment.
requires that the melt remains in contact with the residual rock throughout the melting process.

A

Equilibrium melting

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5
Q

Incomplete chemical reactions may be due to

A

large crystal size, high magma viscosity, and/or low ion migration rates.

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6
Q

The net result of inequilibrium melting is the generation of

A

zoned crystals

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7
Q

Cause of Fractional (disequilibrium)melting

A

melts are separated from the refractory crystals, liquids and crystals do not remain in equilibrium

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8
Q

what happens in fractional melting of rocks containing plagioclase and olivine

A

The early melts are highly enriched in low melting temperature constituents, such as sodium plagioclase and iron olivine.
This leaves behind a more refractory residual solid enriched in calcium plagioclase and magnesium olivine.

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9
Q

Pressure is related to rock depth, whereby 10 km depth corresponds approximately to

A

3.3 kbars.

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10
Q

is the primary means by which basaltic magmas are generated at ocean spreading ridges and continental rifts.

A

Decompression melting of mantle peridotite

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11
Q

Volatiles act as a ____, which is an agent that reduces the melting temperature of a substance.

A

flux

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12
Q

As the degree of partial melting increases, the degree of enrichment of incompatible elements ________.

A

decreases

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13
Q

Light rare earth elements (LREE) are generally less incompatible with solid minerals than heavy rare earth elements (HREE).
T or F

A

F; more incompatible

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14
Q

processes involve changes in bulk magma chemistry after its initial generation.

A

Diversification

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15
Q

includes all processes where the original melt evolves into one or more melts with a different composition, without material being exchanged with an external source.

A

Closed-system diversification

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16
Q

Father of Modern petrology

A

Norman Bowen

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17
Q

The subject of study in Bowens reseach

A

Palisades Sill

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18
Q

When discontinuous and continuous reactions in magmas do not reach completion under equilibrium, chemical variations are preserved in crystals, leading to the formation of

A

zoned crystals and reaction rims.

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19
Q

show a systematic chemical variation from the core to the edge, recording incomplete continuous reactions between the crystal and surrounding melt.

A

Zoned crystals

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20
Q

occur when a new mineral forms around the edges of a crystal with a partially resorbed core.

A

Reaction rims

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21
Q

Crystallization along the walls of the magma chamber in which crystals preferentially form and adhere to the edges results in

A

marginal accretion.

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22
Q

Heat rises so that the upper margin of the magma chamber may cool relatively quickly.
As a result, __________ results from early crystallization of minerals along the ceiling or roof due to preferential heat loss.

A

roof accretion

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23
Q

___________develops as the magma chamber walls release heat to the relatively cold country rock, generating crystals that adhere to the side margins of the magma chamber.

A

Sidewall accretion

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24
Q

occurs as crystals form along the base of the magma chamber.

A

Floor accretion

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25
Q

Because they lose heat rapidly to the wall rocks, pluton margins adjacent to cool country rock commonly display finer grained ____________ compared to the coarser grained crystals of the pluton interior.

A

chilled margins

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26
Q

includes fractionation processes that occur when crystals develop with significantly different densities than the surrounding magma.

A

Gravitational separation

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27
Q

occurs when higher density, ferromagnesian crystals settle to the base of a magma chamber relative to the lower density liquid magma.

A

Crystal settling

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28
Q

can occur if early formed crystals, such as plagioclase, are less dense than the magma.
As a result, crystals may float towards the roof of a magma chamber, effectively segregating them from the remaining melt.

A

Crystal flotation

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29
Q

segregation occurs whereby liquids and crystals are segregated due to factors such as velocity, density, or temperature.

A

Convective flow

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30
Q

Cooling can be accompanied by deformation whereby crystals are compacted and rotated while liquids experience expulsion.
This variation on crystal–liquid fractionation involves a set of processes under the umbrella of

A

filter pressing.

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31
Q

In _________, one parent magma fractionates to produce two or more distinctly different daughter magmas with different compositions.

A

liquid fractionation

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32
Q

Liquid fractionation processes include

A

differential diffusion and liquid immiscibility.

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33
Q

involves the preferential diffusion of select ions within the magma in response to compositional, thermal, or density gradients as well as water content.

A

Differential diffusion

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34
Q

also called liquid–liquid fractionation, occurs when magma separates into two or more distinct immiscible liquid phases.

A

Liquid immiscibility,

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35
Q

How does carbonitite form

A

CO₂ exsolves as a separate fluid phase from alkalic magmas, generating a carbonate-rich fluid which crystallizes as a carbonatite.

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36
Q

processes such as assimilation, magma mixing, and magma mingling involve chemical changes due to interaction of magma with the surrounding country rock or with other magmas entering the system

A

Open-system

37
Q

occurs whereby the surrounding wall rock (country rock) is intruded by and reacts chemically with the magma.

A

Assimilation

38
Q

Forceful injection of magma commonly fractures the surrounding wall rock by a process called .

A

stoping

39
Q

involving multiple magma injections over time, produces complex relationships and constitutes an important diversification mechanism.

A

Magma replenishment,

40
Q

occurs when two or more dissimilar magmas coexist, displaying contact relations but retaining their distinctive individual magma characteristics.

A

Magma mingling

41
Q

implies thorough mixing so that the individual magma components are no longer recognizable.

A

Magma mixing

42
Q

consists of genetically related magmas that have changed composition from a common original parental magma

A

magma series

43
Q

Igneous rock series include:

A

(1) alkaline (or alkalic), and (2) sub-alkaline assemblages.

44
Q

have high Na₂O and K₂O concentrations compared to SiO₂ and are generally undersaturated with respect to SiO₂.

A

Alkaline rocks

45
Q

rocks have moderate to high Na₂O, K₂O, and SiO₂ concentrations.

A

Calc-alkaline

46
Q

have low Na₂O and K₂O but high FeO and CaO concentrations.

A

Tholeiites

47
Q

provide a means to concisely and clearly display rock chemistry variations between samples collected in an area with an eye to establishing their origins and relationships.

A

Variation diagrams

48
Q

are bivariate diagrams in which the vertical ordinate (y-axis) represents weight percents of major or minor oxide compounds such as FeO, MgO, CaO, Na₂O, K₂O, or TiO₂.

A

Harker diagrams

49
Q

If Harker diagrams display smooth, curvilinear trends for all rock data points, then the following three inferences can be made:

A

The rocks are genetically related.
Major element variations reflect a liquid line of descent from a common source in which diversification caused major elements to either increase or decrease progressively with respect to variations in weight percent SiO₂.
The parent magma from which the rocks are derived has a composition near that of the sample with the least SiO₂, that is, of basaltic composition

50
Q

In ____________ trace element concentrations on the abscissa are plotted relative to a standard reference for each element on the ordinate.

A

spider diagrams,

51
Q

The standard reference of spider diagrams may include

A
  • chondrite meteorites,
  • primitive mantle,
  • N-MORB
  • E-MORB
  • ocean island basalt
52
Q

depletion of europium indicates

A

plagioclase fractionation from the melt, which effectively removes europium from the magma.

53
Q

europium enrichment would indicate

A

assimilation of plagioclase components into the melt.

54
Q

Upon fractionation, ____ magmas record a progressive decrease in iron and magnesium with increasing SiO₂ and alkali concentrations

A

calc-alkaline

55
Q

The calc-alkaline series consists largely of

A

andesite, dacite, and rhyolite, as well as high alumina basalt (16–20% Al₂O₃)
(BADR series)

56
Q

The rocks in convergent margin volcanoes are known colloquially as

A

BADR series for the basalts, andesites, dacites, and rhyolites that occur in them.

57
Q

With increasing fractionation, tholeiitic magmas experience _at low to moderate SiO₂ concentrations

A

iron enrichment

58
Q

Alkaline magmas and rocks are highly enriched in _______________ and are less common than calc-alkaline or tholeiitic magmas.

A

Na₂O and/or K₂O

59
Q

Alkaline rocks can contain equilibrium quartz.

A

FALSE

60
Q

Amphibole minerals in alkaline magmas include

A

riebeckite and richterite.

61
Q

Pyroxene minerals found in alkaline rocks include

A

aegerine, aegerine-augite, and spodumene.

62
Q

Alkaline rocks occur in diverse environments:

A

Stable cratonic interiors
Continental rifts (Bailey, 1974)
Ocean islands away from spreading centers (Sorensen, 1974)
Subduction zones (Burke et al., 2003

63
Q

Tholeiitic magmas are typically produced by

A

extensive partial melting of mantle rocks at relatively higher temperatures and lower pressures, often from a depleted source

64
Q

Alkaline magmas are more likely to form through ______________________________ particularly from an undepleted or enriched mantle source

A

limited partial melting (less than 10%) of the mantle at higher pressure conditions

65
Q

consist of large amounts of both silicic (rhyolite-dacite) and basic (basalt) rocks, but have very few intermediate (andesite) rocks.

A

Bimodal suites

66
Q

The tectonic environments where magma series occur in summary

A

Calc-alkaline magmas: Convergent margins.
Tholeiitic magmas: Ocean spreading centers, continental rifts, backarc basins, ocean islands, and hotspots.
Alkaline magmas: Hotspots, ocean islands, and rift environments.
Bimodal volcanism: Continental rifts.

67
Q

is the major mechanism by which continental crust has grown since the Archean, over 2.5 billion years ago

A

Batholith emplacement along convergent plate boundaries

68
Q

Normal zoning within a pluton is characterized by a

A

basic rim and a silicic core.

69
Q

A ___________ is a tabular, concordant pluton that parallels country rock

A

sill

70
Q

Sills develop through ____

A

the injection of magma along a plane (e.g., bedding, foliations) of weakness parallel to the layering in the country rock.

71
Q

Sills commonly form in__________ magmas and are generally _________ in thickness.

A

low-viscosity; < 50m

72
Q

is a blister-like concordant pluton characterized by a flat floor and domed roof

A

A laccolith

73
Q

Laccoliths were first described in the _of Utah by G. K. Gilbert in the 1870s.

A

Henry Mountains

74
Q

are dish-shaped to funnel-shaped concordant plutons that resemble a champagne glass in cross-section view

A

Lopoliths

75
Q

The Bushveld Complex has a length of ___ and is up to_____ thick.

A

550 km; 8 km

76
Q

The champagne-glass lopolith structure can develop due to one or more of the following mechanisms:

A

Meteorite impact and associated crustal melting, as has been suggested for the Sudbury Complex.
Normal faulting and crustal melting associated with rifting, as in the Koillismaa Complex.
A sill-like structure that receives upwelling magma from a conical feeder tube, which would correspond to the stem in the champagne glass.

77
Q

Veins can occur in great abundance, resulting in

A

vein swarms.

78
Q

are cylindrical plutonic dikes exposed at the surface by subsequent erosion.
They represent ancient ______________________ that has long since been removed by erosion.

A

Necks
conduit pipes that funneled magma upward to a volcano

79
Q

Notable examples of volcanic necks include _______________ which has a central neck with radiating dike ridges, and _______ , which preserves radial columnar jointing.

A

Ship Rock, New Mexico,; Devil’s Tower of Wyoming

80
Q

are carrot-shaped, cylindrical pipes that can extend to depths of 200 km (Figure 8.19).
develop via _____________________

A

Diatremes; explosive intrusions that originate deep within the mantle.

81
Q

are tabular intrusions that cross-cut country rock layers.

A

Dikes

82
Q

consist of multiple dikes that can occur in parallel, sub-parallel, radiating, concentric, or random orientations.

A

Dike swarms

83
Q

are typically produced when vertical forces related to rising magma produce fractures that radiate outward from the central vent.

A

Radial dikes

84
Q

are circular in map view and resemble ring dikes, except that they converge at depth in cross-section view.

A

Cone sheet dikes

85
Q

sets consist of parallel, offset dikes that form in response to shear.

A

En echelon dike

86
Q

sets form perpendicular to extension and are particularly common in rift environments.

A

Parallel dike

87
Q

Steeply inclined _________________, composed of gabbro, diabase, and basalt, form layer 2B of the ocean floor at ocean spreading ridges (Figure 8.23).

A

sheeted dikes

88
Q

Sheeted dikes form by the

A

cooling and contraction of magma as it is injected into extensional fractures in oceanic rift valleys.

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