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GLE 2024 (Day 2) > IGNEOUS PETROLOGY (ROCK MELTING) > Flashcards

IGNEOUS PETROLOGY (ROCK MELTING) Flashcards

1
Q

Partial Melting

A

Anatexis

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2
Q

Partial Melting Produces

A

1) Melt with Low Temp constituent
2) Resitite enriched in higher temp refractory elements

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3
Q

Heat Source of Earth

A

1) Heat realeased from the early accretion and differetiation
2) Heat generated by radioactive Breakdown of Unstable Nuclides

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4
Q

Modes of Heat Transfer

A

1)Radiation - waves
2) Conduction - Direct Contact
3) Convection - Fluid caused by molecular motion

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5
Q

?A type of melting in which no other chemical components are neither added or removed from the environment
?Requires continuous contact between the melt and restite
?Over all composition of the system remains the same with evolving compositions of the melt and solids

A

Equilibrium Melting

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6
Q

What can cause incomplete equilibrium Melting

A

Large Crystals
High Viscosity
Low ion migration

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7
Q

What can be produced by incomplete equilibrium melting?

A

Zoned Crystals

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8
Q

Implies that Solids and Melt SEPARATE into isolated fractions that do not continuously react together during the melting process as is for equilibrium melting

A

Fractional Melting (Disequilibrium Melting)

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9
Q

With small degrees of partial fractional melting of ferile source rocks , the melt is said to be enriched in

A

Low Temp Constituents

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10
Q

High degress of partial melting will

A

Deplete the melt with low temp constituents thus becoming more evolved

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11
Q

Factors in Partial Melting

A

1) increase in temp
2) Decompression
3) Induced Volatilization

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12
Q

sloping line of increasing temperature with depth

A

Geothermal Gradient

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13
Q

Is geothermal gradient uniform vertically or laterally?

A

Neither

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14
Q

Geothermal Gradient

A

25 degC/km for the upper 10km

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15
Q

Geothermal Gradient in Old Continental Lithosphere

A

5-10 degC/km

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16
Q

Geothermal Gradient in hotspots, MOR, Volcanic Arcs?

A

30-50 degC/km

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17
Q

Another term for decompression melting?

A

Adiabatic Melting

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18
Q

Pressure within that corresponds to 10Km depth

A

3.3 Kbars

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19
Q

Explain decompression melting

A

Since melting temperature is proportional to pressue,
Decrease in pressure within lithospheric thinning in externsional environments effectively decrease melting temp of rocks

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20
Q

What type of melts are produced by adiabiatic melting of Mantle Peridotites?

A

Basltic Magmas at MORs and Continental Rifts

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21
Q

an agent that reduces the melting temperature of a material or substance

A

Flux

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22
Q

Why does increase in volatile content induce partial melting?

A

Increase in H2O causes the bonds in silicates to weaken (Network Modifier) thus progressively lowering the melting teperature

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23
Q

Other effects of addition of H2O in terms of melting?

A

?Allows rocks to melt over a wide range of temperature regardless of lithostatic pressure
?Melts are less mafic than the source rock due to decreased amounts of FeO and MgO

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24
Q

What minerals are dehdyrated that caused the partial melting of the Mantle Wedge through Induced Volatilization

A

Amphibole
Mica
Serpentine

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25
Q

at what depths would devolatilization of the subducting slab occur?

A

80-150 km

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26
Q

Describe the composition of the Melt/Daughter Magma during anatexis

A

Eriched in Low Temp Constituents which includes incompatible elements such as the Large Ion Lithophile Elemets (LILEs) SiO2, K2O, Na2O

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27
Q

What rocks can form from the crystallization of the daughter magma?

A

Silicic w/ qtz, kfelds and Na Plag

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28
Q

Describe the composition of the Restite or Residual rock durng anatexis

A

Enriched in High Field strength Elements with CaO and MgO

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29
Q

Explain the effect of degrees of partial melting to enrichment

A

The higher the partial meltig the more the magma will be depleted with incompatible elements.

Incompatible elements are only enriched in low degrees of partial melting

30
Q

which of the Rare Earth Elements are incompatible REEs?

A

Light REEs (La-Sm)

31
Q

HREEs

A

Eu-Lu

32
Q

Generalized Product of Melting in varying parent rocks

A

Partial melting will produce a 1 step more silicic melt compare to more basic parent rock

33
Q

Process whereby early formed crystals are segegated from the remaining melt and is a closed system differentiation

A

Fractional Crystallization

34
Q

Father of Modern Petrology who suggested that fractionation may be accomplished through the relative movement of crystals and liquid

A

Norman Levi Bowen

35
Q

The rock formation that was used as a model by Bowen to demonstrate crystal fractionation

A

Palisades Sill

36
Q

A model based on the crystallzation sequence of major igneous minerals

A

Bowens Reaction Series

37
Q

When Foresterite crystallizes removing MgO in the discontinuous rection what would be produced?

A

Enstatite

38
Q

A systematic pattern of chemical variation from the periphery of the crystal towards its center recording an incomplete continuous chemical reaction between the crystal and the surrounding melt

A

Zoned Crystals

39
Q

A display of new mineral along the crystal periphery that surrounds a partially resorbed core composed of a different mineral which indicate Incomplete Discontinuous chemical reactions between the crystal and the surrounding melt

A

Reaction Rims

40
Q

Models for Fractional Crystallization Process

A

1) Marginal Accretion
2) Gravitational Separation
3) Convective Flow
4) Filter Pressing

41
Q

When magma chamber loses heat due to convection to adjacent coutry rocks and crystals tend to form on the margin

A

Marginal Accretion

42
Q

of all the Marginal accretion, which forms first?

A

Roof
Sidewall
Floor

43
Q

Pluton margins adjacent to cool country rocks form this fine grained fabric

A

Chilled Margins

44
Q

This mechanism of fractional crystallization occur when crystals develop have different density than the surrounding magma

A

Gravitational Separation

45
Q

Occurs when higher density ferromagnesian minerals settle to the base of a magma chamber relative to the lower density of the melt thus forming discrete layers of crytsal mush

A

Crystal Settling

46
Q

Occyrs when early formed less dense crystals like plagioclase float towards the roof of the chamber effectively seperating them from the remaining melt

A

Crystal Flotation

47
Q

What impedes Gravitational Separation?

A

High Viscocity

48
Q

Occurs whereby liquid and crystals are segregated due to Velocity, density, or temperature variations

A

Convective Flow Segregation

49
Q

In convective flow segregation, how are melt-liquids fractionated?

A

Magmga should be LOW VISCOUS in order to have variations in convective flow velocity.
?Dense Minerals will tend to accumulate in regions of High Velocity
?light minerals will be concentrated on areas of low velocity

50
Q

How are convective flows in mamba chamber generated?

A

By Differential heat loss from the peripheries/margins to the center

51
Q

Happens in late stage cooling of the magma chamber where crystals are compacted and rotated while liquids experience expulsion to the countryrocks

A

Filter Pressing

52
Q

Processes of Fractional Crystalliztaion

A

1) Marginal Accretion
2) Crystal Settling and flotation
3) Convective Flow Sergregation
4) Filter pressing

53
Q

two processes which can produce two different distinct daughter magmas from one parent magma

A

1) Differential Diffusion
2) Liquid Immiscibility

54
Q

Explain Differential Diffusion

A

?Preferential movement of select ions or favored ions wihitn the magma in response to therma, compositional, or density gradients as well as water content
?plays an important role in transport and concetrtaion of metallic ore minerals in plutonic systems

55
Q

A process wherein a parent magma may segragate in two separate daughter magmas of different composition upon cooling

A

Liquid Immiscibility

56
Q

Common magma immiscible pairs

A

Granitic-Basaltic
Sulfide-rich - Silicate -rich
Alkali-rich - Carbonate-rich

57
Q

Open system differentiation processes

A

1) Assimilation
2) Magma Mingling and Mixing

58
Q

Occurs where the surrounding wall rock is intruded by and reacts chemically with the magma

A

Assimilation

59
Q

Controls of Assimilation process

A

Surface area, larger the surface area the more extensive the exchange of chemical components

60
Q

Process of fracturing the surrounding wall rock by forceful injection of magma

A

Stoping

61
Q

Country rock fragments that is assimilated in the magma

A

Xenoliths

62
Q

Foreign crystal not generated by crystallization of the surrounding magma

A

Xenocrysts

63
Q

Injection of magma to the chamber

A

Magma Replenishment

64
Q

Occurs when two or more dissimilar magmas coexist in a single chamber, displaying contact relations but retaining their distinctive characteritics
(Interject but do not combine)

A

Magma Mingling

65
Q

Evidence of Magma Mingling of felsic and mafic magmas

A

Marble Cake Appearance

66
Q

Homogenization inhibitor

A

Temp Contrast
Density Contrast
Viscosity Contrast

67
Q

This implies interjection of two dissilimar magmas with thorough mixing so that individual magma components are no longer recognizable

A

Magma Mixing

68
Q

Example of Magma Mixing of felsic and mafic magma

A

Intermediate Magma

69
Q

What can serve as evidence for magma mixing

A

Disequilibrium Mineral Assemblage

70
Q

Environments of Magma Mixing

A

Continental Rifts
Convergent Plate Boundaries

GLE 2024 (Day 2) (41 decks)

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