~25 minute (30 point) Questions
1. Describe the crystallization in a binary system with no solid solution and a reaction point (e.g. Fo-SiO2 or kalsilite-quartz as in homework problem 4). You will be asked specific questions about compositions and temperatures of various events and their consequences.
2. Describe the crystallization in a ternary system (e.g. Di-Ab-An or Cpx-Ol-Plg). You will be asked specific questions about compositions and temperatures of various events and their consequences. Doing homework problem 6 will help you to answer this question.
3. Basaltic rocks are commonly classified as alkali olivine basalts
or tholeiitic basalts. Discuss the basis of this classification using
an argument based on phase relationships of the main minerals of basalts.
Give an example of minerals and textures of basalts that support this argument.
~15-minute (20 point) questions
1. Describe the crystallization in a binary system with complete solid solution (e.g. Ab-An, Fo-Fa etc.)
2. How can the phase diagrams on p.103 of your text book explain the difference between hypersolvus granites and subsolvus granites? What are the petrogenetic significance of each type of granite? How would you distinguish them in hand sample?
3. Relate the relationships of minerals that you observe in a thin section (I'll provide a diagram) with the crystallization path that you can trace in a ternary phase diagram (either for primitive melts or evolved melts).
4. Given a set of data on radio nuclides related the Rb-Sr system for a set of rocks, plot the isochron, determine the slope, and intercept, and determine the age of the rocks and the initial 87Sr/86Sr ratio. You will be given graph paper for this question but a calculator would be handy. Discuss your results. See homework problem 3 as an example for this exercise.
~8-minute (10 point) questions
1. Discuss how the europium anomaly in both the lunar highlands (a positive europium anomaly) and the mare basalts (a negative europium anomaly) can be explained by the formation of a global "magma ocean" on the Moon 4.5 billion years ago.
2. Give the correct chemical formula for a group of 10 common rock-forming minerals.
3. How does Bowen's Reaction series (Fig 7-14 in your test) relate to the three suites of rocks (gabbros, basalts, granites) that you have seen in your laboratory? What can you say about temperature of formation and degree of evolution of these rocks from this simple analysis?
4. Classify a large number of plutonic rocks on the basis of their quartz,
plagioclase, and orthoclase content (plus various other minerals
that they contain). You will be given a diagram similar to Fig. 2.2
of your text. See homework problem 1 for sample data.
[Hint: be sure to recalculate the values so the the sum of the end
members on the diagrams equals 100%].
5. Classify a large number of volcanic rocks on the basis of their chemical composition using an alkalis vs. silica diagram like Figure 2-4 of your text.