GLY306                                                                                                               Petrology

Study Questions for Exam IV 20 point questions

1. Be prepared to interpret plots that illustrate some of the following relationships for carbonate or untramafic protoliths.

A. Decarbonation reactions.
B. Dehydration reactions.

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

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

4. Identify the metamorphic facies associated with various minerals plotted on an CaO-SiO₂-MgO diagram.

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

6.  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.

7.  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.

8. Magmas may originate from sources with greatly different compositions and origins.  For the following source rocks: oceanic crust, eclogite, and mantle wedge:
    A. List the three most abundant minerals in order of decreasing abundance
    B. The approximate weight percentage of SiO₂, K₂O, MgO, and CaO
    C. Indicate the tectonic environment in which these rocks would partially melt to produce magmas.

(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. Plot some metamorphic minerals an CaO-SiO₂-MgO triangular diagram.

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

5. Balance a metamorphic reaction for rocks derived from a carbonate or ultramafic protolith, given the minerals involved. (Only  minerals with  simple compositions will be given.)

6. Discuss the three mechanisms by which the mantle can undergo partial melting to produce basaltic magmas.  Give examples of geological environments where
each type is manifest.

7. Explain how a specific phase diagram would govern the melting of a rock of specific composition (e.g. using the system of olivine-SiO₂ polymorph or another
similar system with an eutectic or cotectic).

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