ES 4971-4973 Petrology
Homework 10 Ch 21-22
Name _____________________
1. Metamorphism typically occurs between about 10 and 50 km of
depth. The minerals
a. melt
b. do not melt
2. Compare the geothermal gradients of ocean lithosphere to continental
lithosphere.
a. It gets hotter faster with depth in continental lithosphere
b. It gets hotter faster with depth in ocean lithosphere
3. Explain the difference between lineation and foliation
4. In a continent-continent collision, the micas in schists formed from
mudrocks are oriented
a. ~horizontal-parallel to original bedding planes
b. ~vertical – roughly perpendicular to bedding
5. About slide 21. Look at Figure 21-8. There is a small circle drawn just
above and left of the Key, indicating “Barrow’s Area”. Explain why
this was a clever place to choose as a field site.
6. Again for Figure 21-8, notice that the area to the north “Buchan” near
Banff has only three phases. Refer to the Kyanite-AndalusiteSillimanite PT phase diagram on slide 23 and explain what caused the
difference compared to Barrow’s five index mineral zones.
7. Look at slide 28 on New England metamorphism, and also refer to the
index minerals chart. We expect the greatest pressures at the suture in
a continent-continent collision.
a. the highest metamorphic grades are to the East
b. the highest metamorphic grades are to the West
8. (near slide 30) Which metamorphic facies includes the greatest
pressures?
a. Eclogite
b. Granulite
9. (near slide 33) As Amphibolite passes to depths deeper than about
150km, it becomes Eclogite, and the water in the amphiboles is given
off by the reaction. Water is less dense than surrounding rocks, and it
rises through the mantle wedge above. The water
a. lowers the melting point of minerals in the mantle
b. raises the melting point of minerals in the mantle
10.
Define the following. Some are repeats.
Cleavage (in rocks), schistocity, gneissose structure, Schist,
Greenschist, Amphibolite, Serpentinite, Ophiolite suite,
Blueschist, Glaucophane, Eclogite, Granoblastic, Skarn,
Migmatite, Augen, Porphyroblastic, orthogneiss, paragneiss.