Chapter 7

Question 1

metamorphism

Answer 1

processes of change that a rock undergoes when exposed to physical and chemical conditions significantly different from those that it formed from

Question 2

metamorphic rock

Answer 2

end product of a rock that undergoes metamorphism

Question 3

protholith

Answer 3

parent rock

Question 4

texture of the protholith may change due to:

Answer 4

Recrystallization (when small grains of a mineral coalesce to form larger grains)
Pressure solution (if water is present, some minerals dissolve and the dissolved ions re-precipitate changing relationship between grains)
Alignment of grains (the result is foliation and lineation)

Question 5

mineralogy of the protholith may change by

Answer 5

phase change: one polymorph changes to another more stable at the new conditions {there is no change in the chemical composition}
Neocrystallization: process of chemical reactions between protholith minerals during which ions from two or more minerals combine to create new minerals

Question 6

diffusion

Answer 6

As temperatures rise, atoms vibrate more rapidly, and chemical bonds holding the atoms into the lattice of minerals begin to stretch and break, the freed atoms migrate slowly through the solid rock

Question 7

Lithostatic pressure

Answer 7

results from the burial within the Earth and in all equal directions
lots of pressure at great depths

Question 8

phase change

Answer 8

a new mineral with a more compact atomic arrangement can form that is more stable under the high-pressure conditions

Question 9

polymorphs

Answer 9

minerals like diamond and graphite that have identical compositions but different internal structures

Question 10

directed pressure

Answer 10

also called differential stress

type of pressure in a rock due to vise-like squeezing and or shear

Question 11

phase diagram

Answer 11

has pressure and depth on the vertical axis and temperature on the horizontal axis

Question 12

hydrothermal fluids

Answer 12

rocks that contain high-temperature liquids, gases, and ions of other elements have been dissolved
May be released from magma when the magma solidifies

Question 13

metasomatism

Answer 13

when the chemical composition of a metamorphic rock changes significantly due to reaction with hydrothermal fluids

Question 14

Contact metamorphism

Answer 14

occurs where rocks are subjected to elevated heat without a change in pressure and without the application of differential stress
happens when an igneous intrusion comes in contact with a rock

Question 15

Regional metamorphism

Answer 15

occurs where rocks in a large region of crust are subjected to increases in temperature and pressure and differential stress
happens during mountain building

Question 16

Burial Metamorphism

Answer 16

happens when rocks are simply buries very deeply by overlying sediment

Question 17

Dynamic metamorphism

Answer 17

rock undergoes differential stress in response to shear along a fault zone but does not undergo a change in temp or lithostatic pressure

Question 18

Shock metamorphism

Answer 18

where a meteorite hits the Earth

enormous kinetic energy is converted to heat and differential stress

Question 19

Metasomatism

Answer 19

where hydrothermal fluids are present

Question 20

Classes of metamorphic rock

Answer 20

Aluminous
Quartzo-Feldspithic
Calcareous
Mafic
Organic

Question 21

preferred orientation

Answer 21

foliation and lineation

Question 22

foliation

Answer 22

if it contains a stack or parallel feature alternating bands of different material

Question 23

lineation

Answer 23

rod shaped minerals are aligned parallel to one another

Question 24

Slate

Answer 24

low grade metamorphosed shale or mudstone

Question 25

phyllite

Answer 25

a grade higher than slates

Question 26

schist

Answer 26

medium to high grade rock with a strong folitation

Question 27

Gneiss

Answer 27

high grade metamorphic rock of any composition minerals segregate into light and dark layers

Question 28

Anthracite coal

Answer 28

black shiny hard rock made of carbon that has no visible mineral grains and low specific gravity

Question 29

metamorphic grade

Answer 29

a broad, informal approximation of how much a rock has changed

Question 30

grain size

Answer 30

increases with increasing metamorphic grade

Question 31

porphyroblasts

Answer 31

minerals grow much larger than others in the rock
the larger the mineral the higher the metamorphic grade and the longer the rock stayed at its peak metamorphic temperature

Question 32

gnessic banding

Answer 32

compositional banding defined by alternating light and dark colored layers

Question 33

porphyroclasts

Answer 33

leftover grains of feldspar after the surrounding rock has changed into a mass of fine mica

Question 34

metamorphic index minerals

Answer 34

minerals that therefor indicate the conditions of metamorphism