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Geology > Petro Lecture Final > Flashcards

Petro Lecture Final Flashcards

1
Q

Define Metamorphism

A

a subsolidus process leading to changes in mineralogy and/or texture

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2
Q

What are the effects of increasing temperature in metamorphic reactions

A

Promotes recrystalization, drives reactions, and overcome kinetic barriers

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3
Q

How are upper and lower limits of metamorphism defined

A

Upper limits begins when the rock begins to melt. Lower limit begins when the tem or pressure is too low for crystals to form.

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4
Q

Are the upper and lower limits the same for different protoliths

A

No, the crystal formation varies on composition

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5
Q

Explain how and why the lithostatic and hydrostatic pressure gradients are different

A

Lithostatic: vertical gradient of pressure caused by a column of ROCK
Hydrostatic: vertical gradient of pressure caused by a column of WATER

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6
Q

Describe the three types of deviatoric stress

A

Compression
Tension
Shear

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7
Q

Order of Stress for Lineation

A

Max= intermediate >min
Sausage

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8
Q

Order of stress of Foliation

A

Max>intermediate=min
cookie

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9
Q

order of Stress of Lineation-foliation

A

Max>intermediate>min
soap

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10
Q

How are fluids involved in metamorphism

A

In fluid inclusions, and for hydrous and carbonate phases

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11
Q

How are fluids involved in metamorphism

A

Fluid inclusions
Fluids required for hydrous and carbonous phases

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12
Q

What are the sources of fluid in metamorphism

A

Meteoric, juvenile magmatic, subducted material, trapped sea brine, degassing of the mantle

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13
Q

Where in the US is the highest enhances geothermal potential? Why? How is metamorphism involved?

A

West (yellowstone)

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14
Q

Dynamic Metamorphism

A

deviatoric stress in dominant, deformation and recrystallization are the main process

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15
Q

Thermal metamorphism

A

temperature in a near static stress field

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16
Q

Dynamothermal metamorphism

A

both temp and deformation

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17
Q

Hydrothermal Metamorphism

A

hot water rich fluids, usually involves metasomatism

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18
Q

Fault-zone metamorphism

A

high rates of deformation and strain, minor recrystallization inpact/shock

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19
Q

Prograde metamorphism

A

increase in metamorphic grade with time

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20
Q

retrograde metamorphism

A

decreasing grade as rock cools

21
Q

What governs the size and shape of contact aureole formed around a pluton?

A

Nature of the pluton and nature of the country rock

22
Q

Nature of the pluton examples

A

size, shape, orientation, temp, composition

23
Q

Nature of country rock examples

A

composition, depth, metamorphic, grade prior to intrusion, permiability

24
Q

What two rocks can be formed in fault-zones? Which one is found deep and which one shallow?

A

Fault breccia forms at shallow
Mylonite forms deep

25
Q

What pressure-temperature conditions are Ophiolite soles formed in

A

Low pressure, low medium temp

26
Q

What pressure-temperature conditions are magmatic arcs formed in

A

low pressure, high temp

27
Q

What pressure-temperature conditions are continental rifts formed in

A

High pressure, High temp

28
Q

What pressure-temperature conditions are Craton formed in

A

High pressure, low temp (within the subduction zone range)

29
Q

What pressure-temperature conditions are seafloor formed in

A

low pressure, low to high temp

30
Q

What pressure-temperature conditions are subduction zones formed in

A

High pressure, low temperature

31
Q

The type of protolith involved in a metamorphic event is best grouped based on what characteristics?

A

composition

32
Q

what are some of the common physical weathering processes?

A

Frost wedging, glaciation, joint-sheeting, root wedging, salt wedging

33
Q

What are some common chemical weathering processes

A

dissolution, hydrolysis, oxidation, hydration

34
Q

What are the products of mechanical weathering

A

detrital sedimentary rocks

35
Q

what are the products of chemical weathering

A

chemical sedimentary rocks

36
Q

What minerals have a high mechanical preservation potential

A

quartz, k-spar, plagio, muscovite, protoliths

37
Q

what minerals have a high chemical preservation potential

A

iron oxides, quartz, aluminum oxides

38
Q

What features in grains and lithic fragments in sedimentary rocks are used to narrow down the
possible source area (provenance) of detritus?

A

size (bigger = closer)
sorting (poorly = closer)
roundness (angular = closer)

39
Q

What is a paleosol and why are they important?

A

Ancient soil that can be used to identify geologic contacts and history

40
Q

What is provenance?

A

Source terrain for sediments

41
Q

What is a stromatolite?

A

Structure found in carbonate rock of large laminated microbial accumulations

42
Q

What are the two major categories of sandstone?

A

Arkose and arenite

43
Q

What is the difference between cement and matrix?

A

Both are binding agents but a matrix is always made of mud-shaped grains, cement can be bigger

44
Q

What is the Barrovian Trend

A

chlorite ->biotite->garnet->staurolite->kyanite->sillimanite

45
Q

What is the Buchan Trend

A

Chlorite->biotite->cordierite->andalusite->sillimanite

46
Q

How are isograds defined

A

represents the first appearance of a particular metamorphic index mineral as you progress up the metamorphic grade

47
Q

what is an index mineral

A

a mineral that forms under specific pressure and temperature conditions that provide info on metamorphic history

48
Q

Contact Metamorphism

A

hot magma/liquid touches country rock, deforming it

49
Q

Regional Metamorphism

A

large scale tectonic events that cause widespread metamorphism

Geology (10 decks)

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