Metamorphic Rocks

Question 1

what are metamorphic rocks?

Answer 1

metamorphic rocks are formed from other rocks that are changed because of…

• heat: temp. increases with depth, or contact with igneous intrusions
• pressure: increases with depth
• differential pressure: tectonic activity

Question 2

what are some of the different types of metamorphism?

Answer 2

• regional metamorphism
• contact metamorphism
• hydrothermal metamorphism

Question 3

what is regional metamorphism?

Answer 3

comes from deep burials at high pressures and temperatures, also combined with high lateral pressure at convergent boundaries

Question 4

what is contact metamorphism?

Answer 4

occurs close to igneous intrusions hence high temperature at the surface or shallow depth, hence low pressure

Question 5

what is hydrothermal metamorphism?

Answer 5

hydrothermal or sea-floor metamorphism is associated with the circulation of water through hot fractured rocks at divergent boundaries (often occurs at mid-ocean ridges)

Question 6

what affects the type of metamorphic rock you may have?

Answer 6

metamorphic rocks come in different classes according to where they are formed, and different grades according to the intensity of the heat and/or pressure that have formed them from their parent rocks, then exactly what you get depends upon what the parent rock was

Question 7

what is the grading/scale used for metamorphic rock?

Answer 7

the metamorphic grade: low grade = low temp = low pressure and high grade = high temp >600C = high pressure

Question 8

what can regional metamorphism do to rocks?

Answer 8

change their TEXTURE

Question 9

what are the two types of metamorphic rock?

Answer 9

foliated and non foliated

Question 10

what is the difference between foliated and non foliated rock?

Answer 10

foliated rock has a layered or banded appearance that is produced by exposure to heat and directed pressure, non-foliated rock does not have this appearance

Question 11

what are some common examples of foliated metamorphic rock?

Answer 11

• schist
• slate
• phyllite
• gneiss

Question 12

what are some common examples of non-foliated metamorphic rock?

Answer 12

• hornfels
• marble
• quartzite

Question 13

what is the usual parent rock of marble?

Answer 13

limestone

Question 14

what is the usual parent rock of hornfels? what does hornfels look like?

Answer 14

shale or basalt - hornfels is fine grained, dark and will generally scratch glass, may have a few coarser minerals present

Question 15

some info on schist?

Answer 15

• foliated
• medium grade, regional metamorphic rock
• commonly weak
• micas 35%
• UCS: 20-70 MPa
• SBP: 1-3 MPa

Question 16

some info on hornfels?

Answer 16

• non-foliated
• metamorphic rock
• micas 30%
• UCS: 250 MPa
• SBP: 4 MPa
• strong rock