ES 4971-4973 Petrology
Homework 11 Ch 25-26
Name _____________________
1. George Barrow in 1912 ((Ch 21 section 21.6) recognized zones of
increasing metamorphism (i.e. Chlorite Biotite Garnet Staurolite
Kyanite Sillimanite) in Scottish
a. metapelites (metamorphosed shales)
b. metapsammites (metamorphosed sandstones)
2. Victor M. Goldschmidt (1911, 1912) studied contact metamorphosed
pelitic, calcareous and psammitic hornfelses near Oslo, Norway. He
noticed that the equilibrium mineral assemblage of each metamorphic
rock was chemically equivalent to its original bulk composition. For
example, marbles (e.g. metamorphosed limestones) contain
a. Aluminum-rich and calcium-poor minerals
b. Aluminum-poor and calcium-rich minerals
3. Goldschmidt also noticed that for the reaction
Enstatite + Anorthite  Diopside + Andalusite, the pair
Enstatite + Anorthite was consistently present at Oslo, and noted that
those must have been stable at Oslo when the rock formed
a. True
b. False
4. (near slides 4 & 5) Pentti Eskola (1914, 1915) working on similar
hornfelses in Orijärvi, Finland, confirmed the ideas of Goldschmidt.
Some rocks, however, though chemically equivalent to Oslo,
contained a different mineral assemblage. For example, rocks that
contained Potassium Feldspars + Cordierite + water in Oslo instead
contained the chemically equivalent Biotite + Muscovite + Quartz in
Orijärvi. Eskola, using thermodynamic reasoning (as we did in
Chapter 5) deduced that, since Biotite and Muscovite are more
hydrous, they are stable at lower temperatures (remember heating lab
samples to 100C and 800C for driving out the LOI = loss on ignition
water) , so the Orijärvi rocks formed at lower temperatures. Also since
Biotite and Muscovite + Quartz are a lower volume assemblage, they
are stable at higher pressures, so the Orijärvi rocks formed at higher
Pressures than Oslo rocks.
a. True
b. False
5. (near slide 12) In 1920, Eskola proposed facies for metamorphism of
mafic rocks. Walking from unaltered basalt toward Migmatites, the
metamorphic facies he saw might be Greenschist, then Amphibolite,
then Granulite or Eclogite depending on the Pressure changes.
a. True
b. False
6. Granulites form in
a. wet conditions at medium temperatures
b. dry conditions at high temperatures
7. Fluid inclusions in Granulites are
a. water
b. carbon dioxide
8. Sketch from memory an Ophiolite Suite of rocks, representing the
ocean lithosphere formed at a mid-ocean ridge.
9. Mafic Blueschists are easily recognizable by their color, and are
useful indicators of ancient subduction zones. Their formation
requires abundant
a. halite present near subducted ophiolites.
b. water present near subducted ophiolites.
10.
List two methods for testing proposed P-T-time paths
Chapter 26
11.
In the dehydration reaction
KAl2Si3AlO10(OH)2 + SiO2 = KAlSi3O8 + Al2SiO5 + H2O
Muscovite
+ Qtz = K-spar
+ Sill
+ Water
If the water escapes, Le Châtelier’s Principle says that the reaction
will run to the
a. right.
b. left.