Metamorphism

Question 1

What are four major factors controlling metamorphic processes?

Answer 1

Temperature, Pressure, Pore fluid pressure, Time

Question 2

Where does Earth’s internal heat come from?

Answer 2

Radioactive elements e.g. uranium and potassium

Question 3

Define Heat Flow

Answer 3

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

Question 4

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

Answer 4

Confining pressure

Question 5

Pressure at Depth =

Answer 5

Depth x Density x Acceleration due to gravity

Question 6

What are three places fluids can be found in?

Answer 6

Pore spaces between grains, Tiny cracks and fractures, Veins

Question 7

What are two reasons pore fluids important in metamorphism?

Answer 7

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

Question 8

Define Differential Stress

Answer 8

The difference between the maximum and minimum principal stresses

Question 9

What are the four main types of metamorphism?

Answer 9

Contact, Regional, Burial, Dynamic

Question 10

What five metamorphic rocks come from shale?

Answer 10

Spotted rock, Hornfels, Slate, Gneiss, Schist

Question 11

What metamorphic rock comes from sandstone?

Answer 11

Metaquartzite

Question 12

What metamorphic rock comes from limestone?

Answer 12

Marble

Question 13

What metamorphic rock comes from basalt?

Answer 13

Eclogite

Question 14

Define Aluminosilicate

Answer 14

Very common group of minerals including kyanite, sillimanite and andalusite

Question 15

What metamorphism is kyanite associated with?

Answer 15

Burial metamorphism (high pressure, low temperature)

Question 16

What metamorphism is sillimanite associated with?

Answer 16

Regional metamorphism (high pressure, high temperature)

Question 17

What metamorphism is andalusite associated with?

Answer 17

Contact metamorphism (low pressure, high temperature)

Question 18

Define Polymorph

Answer 18

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

Question 19

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

Answer 19

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

Question 20

Define Granoblastic Crystals

Answer 20

Metamorphic rock with minerals of equal size

Question 21

Define Porphyroblastic Texture

Answer 21

Large crystals set in a finer groundmass

Question 22

Define Poikiloblastic Texture

Answer 22

Poikiloblasts are usually porphyroblasts with pieces of other minerals within them

Question 23

Define Porphyroclastic Texture

Answer 23

Clasts set in a finer matrix, associated with dynamic metamorphism

Question 24

Define Non-Foliated

Answer 24

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

Question 25

Define Foliated

Answer 25

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

Question 26

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

Answer 26

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

Question 27

Define Pelites

Answer 27

Fine grained sedimentary parents like clays, shales and mudstones

Question 28

How do pelites respond to increases in temperature?

Answer 28

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

Question 29

Define Phyllites

Answer 29

Strongly cleaved rocks rich in platy minerals, particularly chlorite

Question 30

Between what temperatures do phyllites form?

Answer 30

250-300 degrees C

Question 31

What are the three types of porphyroblasts?

Answer 31

Post-tectonic, Syn-tectonic, Pre-tectonic

Question 32

Define Post-Tectonic

Answer 32

Forms after the period of deformation

Question 33

Define Syn-Tectonic

Answer 33

Forms during the period of deformation

Question 34

Define Pre-Tectonic

Answer 34

Forms before the period of deformation

Question 35

Define Burial Metamorphism

Answer 35

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

Question 36

Define Isograd

Answer 36

Areas which have had the same amount of metamorphism

Question 37

Define Dynamic Metamorphism

Answer 37

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

Question 38

Define Cataclasis

Answer 38

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

Question 39

What rock is the result of cataclasis?

Answer 39

Mylonite

Question 40

Define Pressure-Temperature-Time Path

Answer 40

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