GLY306                                                                                                        Petrology

Study Questions for Exam III

Plots - Be prepared to plot or interpret some of the following information on a petrogenetic grid like to one pictured below:
 

A. Selected geothermal gradients.
B. Melting curves for granite and basalt.
C. Various facies of metamorphic rocks
D. Anhydrous metamorphic reactions.
E. Decarbonation reactions.
F. Dehydration reactions.

20 point questions

1. Give the common characteristics of Archean teranes.  Show how the Archean rocks of the Superior Province of Canada fits this model.

2. Give the common characteristics of Proterozoic teranes.  Show how the Proterozoic rocks of the Grenville Province of Canada fits this model.

3. Discuss the concept of metamorphic grade as developed by Barrow in the Scottish Highlands.  Define the concept of isograd and plot the minerals used by Barrow on a sketch map of his study area.

4. Identify the metamorphic facies associated with various minerals plotted on an ACF diagram.

5.  Show how a tie-line flip can explain a paired metamorphic reaction that occurs at an isograd.

6.  Write the general metamorphic reactions (not balanced) for an increasing sequence of grade in siliceous dolomites using data from CaO-SiO2-MgO triangles.

7.  Discuss the role of fluids in metasomatism of a ultramafic body in contact with a quartzo-feldspathic rock. The case of Grafton Vt. is a good example.  Make a sketch of the mineral zonation and show what elements are enriched or depleted across the contact.

8.  Discuss the role of fluids in metasomatism of a dolomite in contact with a quartz diorite. Examples from the Italian Alps  would be good. Make a sketch of the mineral zonation and show what elements are enriched or depleted across the contact.

(10 point) questions

1. Plot the zonation of minerals associated with metasomatism of ultramafic pods embedded in regionally metapelites of low grade.  Use the minerals actinolite, antigorite, biotite, chlorite and talc.

2. Compare the mineral sequence in Barrows isograds with those of the Buchan type of metamorphism.  Explain what controls the difference of these sequences.

3. Plot some metamorphic minerals an ACF triangular diagram.

4. Be able to identify pre-tectonic, syn-tectonic, and post-tectonic textures using images of rock textures

5. Write the Gibbs phase rule.  Answer questions on a diagram showing the kyanite-sillimanite-andalucite P-T relationship to explain the relationship of phases to degrees of freedom in this system.

6. Balance a metamorphic reaction given the minerals involved. (Only simple mineral compositions will be given.)