Metamorphic petrology - L1

Question 1

What is metamorphism?

Answer 1

subsolidus process leading to changes in
mineralogy and/or texture and often in chemical composition in a rock

Question 2

What is the metamorphism for pyroxene?

Answer 2

Pyroxene to chlorite

Question 3

What information might be retained with rocks which have undergone metamorphism?

Answer 3

enough inherited information from protolith to potentially determine pre-metamorphic history

Question 4

What is the word for the action of metamorphism?

Answer 4

Metamorphose

Question 5

What can you call rock that has been altered by metamorphism?

Answer 5

the rock has been metamorphosed

Question 6

At what temperature will metamorphism begin?

Answer 6

after diagenesis around 100-150*c

Question 7

What is temperature like around the end of metamorphic range?

Answer 7

at 900*c metamorphism ends and shifts to anataxis

Question 8

What is protolith?

Answer 8

original rock

Question 9

What to factors control the metamorphism?

Answer 9

an increase in pressure and temperature (temp most important)

Question 10

What is the variation of temperature over depth called?

Answer 10

geothermal gradient

Question 11

What are the effects of increasing temp with metamorphism?

Answer 11

Recrystallisation promoted
Increase grain size
Driver of chemical reactions

Question 12

What is the reason for the promotion of recrystallisation due to temp increase with metamorphism?

Answer 12

due to large surface area to volume ratio

Question 13

What happens to grain size during metamorphism due to increased temp?

Answer 13

fine aggregates coalesce to form larger grains

Question 14

What does coalesce mean?

Answer 14

come together to form one mass

Question 15

What variable will lead to increased pressure?

Answer 15

depth

Question 16

How can the physical conditions at depth be described?

Answer 16

temperature-pressure (T/P) coupling

Question 17

How can geological setting affect T/P coupling?

Answer 17

High T/ Low P at or near magmatic intrusion (hot)

Question 18

What is lithostatic pressure stress like?

Answer 18

uniform stress (hydrostatic)

Question 19

Does lithostatic pressure affect the texture of metamorphic rocks?

Answer 19

No no effect

Question 20

What is the pressure like with Deviatoric pressure?

Answer 20

varies in different directions

Question 21

What will deviatoric pressure due to metamorphic rock pressure?

Answer 21

induce characteristic pressure

Question 22

What will deviatoric pressure do to rocks?

Answer 22

induce grain rotation and realignment (perpendicular to mass compression)

Question 23

What texture will deviatoric pressure produce?

Answer 23

fabric (cleavage, schistocity)

Question 24

What can lead to the production of localised metamophism?

Answer 24

shear stress at transform margins

Question 25

What are mylonites?

Answer 25

typical metamorphic rocks found deep at shear zones

Question 26

How do fluids relate to metamorphism?

Answer 26

facilitate metamorphic processes

Question 27

What are the typical fluids related to metamorphic processes?

Answer 27

H2O (most common), CO2, CH4, N2, S

Question 28

What are fluids needed to produce in metamorphic areas?

Answer 28

hydrous carbonate phases

Question 29

What are some examples of fluids required to form some metamorphic rocks?

Answer 29

meteoric ,juvenile magmatic
subducted material, trapped sedimentary brines, or degassing of the
mantle

Question 30

What is the speed of metamorphism like?

Answer 30

solid-state process so very slow

Question 31

How long do large temperature changes needed for metamorphism take?

Answer 31

tens of millions of years

Question 32

How can the long time for large temp change affect metamophism?

Answer 32

frequently cause it to be incomplete so many relics can be found in rock record

Question 33

What cab be used to classify metamorphic rocks?

Answer 33

metamorphic grade

Question 34

How does the metamorphic grade classify metamorphic rocks?

Answer 34

indicates intensity if metamorphism (P/T) without saying exact pressure temp relationship