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NDSU Geosciences Petrology 422/622 Study Questions for Exam 1 Exam 1 will cover Winter Chapters 1, 2, 4, 5, 6, 7, and 8. Optical mineralogy will be covered in the lab exam. Below are some sample questions and topics. You collect fine-grained rocks (a basalt, a rhyolite) and a glassy rock (obsidian). How do you classify these samples using a Q-A-P-F diagram? What is a pyroclastic rock? How is it formed? For a ternary system such as Di-An-Fo or Fo-An-SiO2, write a complete narrative of the crystallization history for a liquid of arbitrary composition. Apply the phase rule to interpret the phase relations. (Winter Ch. 7) For typical igneous systems such as Di-An-Fo or Fo-An-SiO2, etc. know the minerals and their chemical compositions. Provide short definitions (a few words and/or a diagram) of: incongruent melting porphyritic chondritic meteorite silica-saturated mineral mode solvus phase solid solution pillow lava pyroclastic etc. For a generic chemical reaction, how do we use thermodynamics to determine which side of a reaction equation is most stable under a given set of conditions? Discuss and draw supporting diagrams on: the structure and composition of the Earth G vs T (at constant P) for solid and liquid phases of a substance. zoning of plagioclase feldspars during equilibrium vs. non-equilibrium crystallization (remember we discussed this at the end of mineralogy, too) difference between the composition of liquid produced by melting a forsterite-enstatite rock at high pressure and low pressure. difference between crystallizing alkali feldspars at high and low pressure. Harker plots for major and minor elements As you prepare by reviewing the text and your notes, think up similar questions.

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