Chapter 8 - Metamorphism and Metamorphic Rocks

Question 1

Metamorphism

Answer 1

changes in mineral assemblage and texture that take place in rocks due to changes in temperature and/or pressure. These changes happen in a solid state

Question 2

Chemical composition of original rock

Answer 2

determines mineral assemblage (most important factor)

Question 3

Low grade

Answer 3

Low temperature and low pressure

Question 4

high grade

Answer 4

high temperature and high pressure

Question 5

stress

Answer 5

directed pressure

Question 6

uniform stress

Answer 6

equal in all directions - creates igneous rocks - random alignment of materials

Question 7

differential stress

Answer 7

unequal in all directions - creates metamorphic rocks - parallel alignment

Question 8

intergranular fluid

Answer 8

acts as transporting medium and speeds up chemical reactions

Question 9

vein

Answer 9

formed by precipitation of minerals from intergranular fluid into fracture

Question 10

Prograde

Answer 10

rising temperature and pressure with water

Question 11

Retrograde

Answer 11

falling temperature and pressure without water

Question 12

Long periods of time

Answer 12

produce coarse grained rocks with high temperature and pressure

Question 13

short periods of time

Answer 13

produce fine grained rocks with lower temperature and pressure and/or short reaction times

Question 14

migmatite

Answer 14

composite rock - contains igneous and metamorphic components

Question 15

foliation

Answer 15

planar texture - parallel mineral alignment due to differential stress

Question 16

Slaty Cleavage

Answer 16

fine grained rock splits into plate like fragments along planes - low grade - new mineral grains can only be seen with microscope

Question 17

Schistosity

Answer 17

parallel but not necessarily planar arrangement of minerals - high grade - grains can be seen with unaided eye

Question 18

Marble

Answer 18

metamorphic limestone or sandstone

Question 19

Metamorphism of shale and mudstone

Answer 19

Slate (low grade) - phyllite (intermediate grade) - Schist (high grade) - Gneiss (high grade)

Question 20

Quartzite

Answer 20

forms from quartz sandstone

Question 21

Mechanical deformation

Answer 21

high pressure - physical transformation

Question 22

chemical recrystallization

Answer 22

high temperature - change in crystallization

Question 23

Cataclastic metamorphism

Answer 23

uncommon - mechanical deformation with minor chemical recrystallization - elongated grains fragments - foliated

Question 24

contact metamorphism

Answer 24

uncommon - chemical recrystallization with minor mechanical deformation - occurs adjacent to hot magma bodies

Question 25

metamorphic aureole

Answer 25

well defined shell of altered rock adjacent to intrusion (halo)

Question 26

Hornfels

Answer 26

hard, fine grained rock that is formed by contact with small intrusion without fluid

Question 27

Regional metamorphism

Answer 27

most common and widespread - (differential stress) mechanical deformation and chemical recrystallization - distinctly foliated