QUIZ #9
Core Geology 3.32
1. According to the figure below, _______ is the temperature at which melting starts.
A)
B)
C)
D)
E)
200ºC
400ºC
600ºC
800ºC
none of the above
2. Characteristic minerals known as _______ mark the appearance of new mineral
assemblages in the progression from low to high grade metamorphism.
A) isograds
B) index minerals
C) aureoles
D) stress minerals
E) schistosity
3. _______ deformation includes grinding, crushing, bending, and fracturing.
A) Chemical
B) Mechanical
C) Metasomatic
D) Burial
E) Hydrothermal
4. Meteorite impacts can be identified by the presence of _______.
A) stress
B) phyllite
C) slaty cleavage
D) schistosity
E) shocked quartz
5. Lines marking the first appearance of index minerals are known as _______.
A) low grade
B) stress
C) isograds
D) schistosity
E) contour
True/False
6. Slate is a type of a high grade metamorphic rock. FALSE
7. Metamorphic rocks can occur from sedimentary and igneous rocks. TRUE
8. The largest scale of metamorphism results from contact metamorphism. FALSE
9. In the figure below, burial metamorphism occurs at #4. FALSE
Fill-In-The-Blank
10. ______ metamorphic rocks are changed under temperatures of less than 400°C and
pressures of less than 400MPa.
LOW GRADE
11. _______ is a foliation in low-grade metamorphic rocks that causes them to break into
flat, platy fragments.
SLATY CLEAVAGE
12. _______ are composite rocks composed of igneous and metamorphic rocks.
MIGMATITES
Essay
13. What is metasomatism?
Metasomatism are a processes in which the chemical composition of a rock is altered by
the addition or removal of material by soluble fluids. Metasomatism is important in the
formation or ore deposits.
14. Explain the upper temperature limit of metamorphism.
Metamorphic rocks do not melt. The upper temperature limit for metamorphism is
800ºC. Above this temperature, rocks begin to melt, which by definition, is no longer a
metamorphic rock.
15. Explain the difference between low grade and high grade metamorphic rocks.
Low grade metamorphic rocks are formed under temperatures of 400ºC and pressures of
400MPa. High grade metamorphic rocks are formed at temperatures above 400ºC and
pressures higher than 400MPa.
16. What are the factors that control metamorphism?
There are many factors that control metamorphism. These factors include temperature
and pressure. The higher the temperatures and pressures, the higher the grade of
metamorphism. The presence or absence of pore fluids has an affect on metamorphism.
The direction and amount of stress present plays a role in the type and amount of
metamorphism. Finally, the rate and duration of deformation affect the type of
metamorphic rocks that will form.
17. Explain how a geologists use index minerals.
A geologist can identify different grades of metamorphism in the field based on the
presence of specific minerals, called index minerals. Once a specific mineral is
identified, a general temperature and pressure can be assigned. Some of these minerals
include chlorite, biotite, garnet, and kyanite. When these index minerals are identified,
one can get a general idea of the metamorphic history of the rock.