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Geology > Metamorphism > Flashcards

Metamorphism Flashcards

1
Q

What are four major factors controlling metamorphic processes?

A

Temperature, Pressure, Pore fluid pressure, Time

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2
Q

Where does Earth’s internal heat come from?

A

Radioactive elements e.g. uranium and potassium

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3
Q

Define Heat Flow

A

The amount of heat flowing out at the Earth’s surface

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4
Q

What is the main type of pressure in the Earth’s crust?

A

Confining pressure

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5
Q

Pressure at Depth =

A

Depth x Density x Acceleration due to gravity

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6
Q

What are three places fluids can be found in?

A

Pore spaces between grains, Tiny cracks and fractures, Veins

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7
Q

What are two reasons pore fluids important in metamorphism?

A

They act as catalysts and accelerate metamorphic reactions, They act as solvents and so bring ions into contact with each other as they move

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8
Q

Define Differential Stress

A

The difference between the maximum and minimum principal stresses

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9
Q

What are the four main types of metamorphism?

A

Contact, Regional, Burial, Dynamic

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10
Q

What five metamorphic rocks come from shale?

A

Spotted rock, Hornfels, Slate, Gneiss, Schist

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11
Q

What metamorphic rock comes from sandstone?

A

Metaquartzite

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12
Q

What metamorphic rock comes from limestone?

A

Marble

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13
Q

What metamorphic rock comes from basalt?

A

Eclogite

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14
Q

Define Aluminosilicate

A

Very common group of minerals including kyanite, sillimanite and andalusite

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15
Q

What metamorphism is kyanite associated with?

A

Burial metamorphism (high pressure, low temperature)

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16
Q

What metamorphism is sillimanite associated with?

A

Regional metamorphism (high pressure, high temperature)

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17
Q

What metamorphism is andalusite associated with?

A

Contact metamorphism (low pressure, high temperature)

18
Q

Define Polymorph

A

Share the same chemical formula of Al2Si2O5, but they have different chemical structures and therefore different physical properties

19
Q

What three things does the textures in metamorphic rocks depend on?

A

Temperature and pressure conditions, Effect of tectonic stresses, Original texture of the rock

20
Q

Define Granoblastic Crystals

A

Metamorphic rock with minerals of equal size

21
Q

Define Porphyroblastic Texture

A

Large crystals set in a finer groundmass

22
Q

Define Poikiloblastic Texture

A

Poikiloblasts are usually porphyroblasts with pieces of other minerals within them

23
Q

Define Porphyroclastic Texture

A

Clasts set in a finer matrix, associated with dynamic metamorphism

24
Q

Define Non-Foliated

A

Develop where there is an absence of stresses and consequently the minerals show no preferred orientation

25
Q

Define Foliated

A

Show a preferred orientation of the minerals, usually in a direction at right angles to the maximum pressure

26
Q

What are five factors controlling the extent of baking around an igneous intrusion?

A

Size and shape of the igneous body, Composition, Thermal conductivity of the country rock, Volatile content, Distance from igneous body

27
Q

Define Pelites

A

Fine grained sedimentary parents like clays, shales and mudstones

28
Q

How do pelites respond to increases in temperature?

A

Reactions take place quickly for clay minerals and micas due to their large surface area, making them sensitive to the effect of heat and new minerals grow as the temperature rises

29
Q

Define Phyllites

A

Strongly cleaved rocks rich in platy minerals, particularly chlorite

30
Q

Between what temperatures do phyllites form?

A

250-300 degrees C

31
Q

What are the three types of porphyroblasts?

A

Post-tectonic, Syn-tectonic, Pre-tectonic

32
Q

Define Post-Tectonic

A

Forms after the period of deformation

33
Q

Define Syn-Tectonic

A

Forms during the period of deformation

34
Q

Define Pre-Tectonic

A

Forms before the period of deformation

35
Q

Define Burial Metamorphism

A

High pressure/low temperature regional metamorphism associated with convergent plate margins

36
Q

Define Isograd

A

Areas which have had the same amount of metamorphism

37
Q

Define Dynamic Metamorphism

A

They are of local significance only, restricted to narrow zones adjacent to faults and thrusts

38
Q

Define Cataclasis

A

The grinding down of broken rock, producing elongated lens shaped porphyroblasts which tend to show a preferred orientation or lineation

39
Q

What rock is the result of cataclasis?

A

Mylonite

40
Q

Define Pressure-Temperature-Time Path

A

The set of all P-T conditions experienced by a rock during its metamorphic history

Geology (16 decks)

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