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Hefferan > Magma And Intrusive Structures > Flashcards

Magma And Intrusive Structures Flashcards

1
Q

Melting of source rocks

A

Anatexis

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2
Q

requires that the melt remains in contact with the residual rock throughout the melting process. As a result, the overall composition of the system remains the same

A

Equilibrium melting

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3
Q

Implies that solids and melt separate into isolated fractions that do not continue to react together during the melting process.

A

Fractional melting

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4
Q

Earth ’ s average geothermal gradient is?

A

∼ 25 ° C/km for the upper 10km

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5
Q

geothermal gradient variation for old rocks

A

5-10C/km

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6
Q

Geo gradiemd for hotspots

A

30 to 50C/km

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7
Q

Decompression melting, also known as , results from a decrease in pressure.

A

adiabatic melting?

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8
Q

CO, CO2 , OH, SO2 , H2S, NH3 , K2O, Na2O, HCl and HF, as well as the elements H, F, Cl, S, He and Ar

A

Volatiles

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9
Q

A is an agent that reduces the melting temperature

A

flux

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10
Q

H2O, CO2 , K2O and Na2O is the major cause for partial melting in subduction zones. T or f

A

T

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11
Q

original melt evolves into one or more melts with a different composition, without material being exchanged with an external source

A

Differentiation

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12
Q

processes whereby early formed crystals are segregated from the remaining melt

A

Fractional crystallization

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13
Q

father of modern petrology

A

Bowen

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14
Q

Sill studied by bowen

A

Palisades sill

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15
Q

Coarse grained basalt

A

Diabase

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16
Q

indicate incomplete discontinuous chemical reactions between crystals and melts

A

Rxn rims

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17
Q

Bc they do not react with the magma, continuously or discontinuously

A

muscovite, potassium feldspar and quartz

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18
Q

Models for fractional crystallization

A

marginal accretion, gravitational separation, convective fl ow and filter pressing.

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19
Q

Crystallization along the walls of the magma chamber

A

marginal accretion

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20
Q

includes crystal settling and crystal flotation processes

A

Gravitational separation

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21
Q

one parent magma fractionates to produce two or more distinctly different daughter magmas with different compositions

A

Liquid fractionation

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22
Q

Liquid fractionation processes include (2)

A

differential diffusion and liquid immiscibility

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23
Q

involves the preferential diffusion of select ions within the magma in response to compositional, thermal or density gradients as well as water content. Differential diffusion may play a key role in the transport and concentration of metallic ore deposits in plutonic systems

A

Differential diffusion

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24
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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25
Q

Forceful injection of magma commonly fractures the surrounding wall rock by a process called _ . Country rock fragments that fall ( stope ) into the magma are called_

A

stoping, xenoliths

26
Q

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

A

Magma replenishment

27
Q

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

A

Magma mingling

28
Q

marble cake is caused by?

A

Magma mingling

29
Q

implies thorough mixing so that the individual magma components are no longer recognizable. For example, felsic and mafi c magma can mix to produce an intermediate magma

A

Magma mixing

30
Q

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

A

magma series

31
Q

Igneous rock series include: (2)

A

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

32
Q

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

33
Q

subalkaline series can be subdivided into (2)

A

calc alkaline and tholeiite suites

34
Q

rocks have moderate to high Na2O, K2O and SiO2 concentrations

A

Calc alkaline

35
Q

have low Na2O and K2O but high FeO and CaO concentrations

A

Tholeiites

36
Q

Standard references include

A

Chondrite, primitive mantle, NMORB, EMORB, OIB

37
Q

Useful in demonstrating enrichment or depletion of compatible VS incompatible elements

A

Spider diagram

38
Q

Depletion of europium indicates plag fractionation from melt. T or f

39
Q

Enrichment of europium indicates assimilation of plag. T or f

40
Q

Calc alkali series include

A

Dacite, rhyolite, andesite, high alumina basalt(16-50%al2o3)

41
Q

Magmas that dominate convergent e.g. Circum pacific

42
Q

Rocks in convergent margin volcanoes are known as?

43
Q

Al203 (Inc, Dec) with crystallization of ferromag monerals(olivine, Pyro, amphi) then (Inc, Dec) with removal of plag and micas

44
Q

MgO and Fe203 (Inc, Dec) with crystallization of ferromag min

45
Q

Cao (Inc, Dec) with crystallization of Calc plag

46
Q

NaO (Inc, Dec) due to removal of ig MgO Fe203 CaO, then (Inc, Dec) as sodium plag crystallizes in andesitic and more silicic rocks

47
Q

Sio2 and k20 (Inc, Dec) as MgO Fe203 CaO na203 Al203 are progressively removed by crystallization

48
Q

_magmas and basalts dominate extensional envi e.g. Ocean ridges and cont drifts

A

Tholeiitic

49
Q

Tholeiites occur over Hotspot in intra plate settings and in frontal portions of immature (relatively young) volc. Arcs (characterized by thinning crust). T or f

50
Q

Amphi mins from alkaline magmas include

A

Riebeckite, richterite

51
Q

Pryxn mins from alkaline rocks

A

Aegerine, aegirine-augite, spodumene

52
Q

Alkaline rocks

A

Alkali basalts, hawaiite, benmoreite, mugearite, trachyte, nephelinite, phonolite, lamprophyre, carbonatite, komatiite, kimberlite

53
Q

Alkali rocks occurs in?

A

Stable cratonic interior, cont rifts, ocean islands away from spreading centers and subd zones ,

54
Q

Both alkali and tholeiitic magmas occur at hotspots, ocean islands, Rift envi. T or f

55
Q

Calc alkaline occur almost at convergent margins. T or f

56
Q

Tholeiitic magmas generated at ocean spreading centers, in cont rifts, Backarc basins, ocean islands, hotspots. T or f

57
Q

Alkaline magmas occur primarily at hotspots, ocean islands, Rift. T or f

58
Q

Bomodal rifts occur at cont rifts. T or f

59
Q

Magmas of Rift valley

A

Alk and bomodal

60
Q

Volc. Arc magma

A

Calc. Alkali

61
Q

Ocean Island magma

A

Tholeiitic and alkali

62
Q

Ocean ridge magma

A

Tholeiitic

Hefferan (4 decks)

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