METAMORPHISM

Question 1

Metamorphism and types

rock cycle

Answer 1

• rocks that are buried in the geosphere and are affected by: pressure, differential stress and temperature
• creates new minerals from recrystallization
  1. contact,
  2. dynamic,
  3. regional

they combine to deform and recrystalize rocks without melting

meta= beyond

Question 2

solid state stress

Answer 2

• stress is not uniform in all directions.
• can be divided into
  1. * mean stress (acts to change volume)
  2. differential stress (acts to change shape).
• The force concentration varies with direction in a state of stress.

Question 3

Fabric

Answer 3

-alignment of minerals
-this develops if the rock changes shape in response to DIFFERENTIAL STRESS

Question 4

State of stress “equation”

Answer 4

pressure/mean stress + differential stress = state of stress
-pressure can vary in all directions

Question 5

Temperature and in what way does it form meta rocks

Answer 5

• Temperature increases with depth inside the Earth.
• Increasing temperature weakens rocks, encourages recrystallization, and transforms
• the hot magma transfers heat to nearby rocks to cool down and produces new minerals as a result
  -this is the only way for magma to cool

Question 6

Rocks named by fabric

metamorphic rock types

Answer 6

slate, schist, gneiss
-diff stress

Question 7

Rocks based on composition

metamorphic rock types

Answer 7

Quartzite, marble, greenstone

Question 8

mean stress

Answer 8

acts to change volume

Question 9

differential stress

Answer 9

acts to change shape

Question 10

Geothermal gradient

Answer 10

• the rate at which temperature increases with depth.

Question 11

contact metamorphism

Answer 11

• due to heat from nearby magma
• new high temp minerals
• increases grain size
• little fabric
• ex is hornfels

Question 12

regional metamorphism

Answer 12

• high temperature and pressure with differential stress
• occurs at the interior of mountian belts
• strong fabric from deformation caused by diff stress
• past tectonic events

Question 13

dynamic metamorphism

Answer 13

• rocks flow in solid state from response to diff stress
• strong fabric
• reduces grain size
• ex mylonite, conglomerate

Question 14

slate

Answer 14

• fine grained
• formed at low temp
• strong fabric - colour variation and bedding in mudstone
• regional metamorphism

Question 15

schist

Answer 15

• course grained
  *mica minerals
• formed at high temperature
• strong fabric orientation
• regional metamorphism

Question 16

gneiss

Answer 16

• banded
• forms at high temp
• grains visible

Question 17

rocks with no fabric

Answer 17

• quartzite
• marble
• greenstone
• they are all stable

Question 18

quartzite grains and parent rock

Answer 18

*metamorphosed sandstone
* interlocking quartz grains
* stable

Question 19

marble

Answer 19

• mainly carbonates
• metamorphosed limestone
• course interlocking calcite crystals

Question 20

greenstone

Answer 20

• metamorphosed mafic volcanic rock - basalt
• high temps
• ferro-magnesium silicates- olivine

Question 21

rock cycle summary

Answer 21

• describes the processes of partial melting, magma formation, weathering, erosion, sedimentation and metamorphism
  *subduction as a process returning crust to the mantle

Question 22

subduction

Answer 22

returns crust to the mantel

Question 23

rock cycle process

Answer 23

magma cools to make igneous rock, erosion and weathering = transport of material- deposited as a sediment - undergoes diagenesis+lithification= sed rock - rocks may be buried then subject to heat press and deformation= metamorphic rock - if hot enough partial melting may produce magma.
* if metamorphic rock isnt returned to mantle it skips straight to weathering
* igneous can skip to metamorphism

Question 24

partial melting

Answer 24

• brings magma to the crust from uplift
• or at high temps of metamorphism

Question 25

protolith

Answer 25

of a metamorphic rock is the type of rock prior to metamorphism