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Lab 423/623 Syllabus


NDSU Geosciences Petrology 422/622
Study Questions for Exam 2

Since the last exam, we have covered most of Winter chapters 9-11. Additional material (mostly dealing with partial melting) was covered with the aid of handouts.

Below are some sample questions and topics.

Topics in phase equilibria

  1. extracting information from a ternary phase diagram (primary phase to crystallize for a given liquid composition; perititectic behavior, compatible phases for a given T, etc.)
  2. crystallization and melting in ternary systems (example: the fo-en-di system)
  3. batch vs. fractional melting (handouts)
  4. the Gibbs phase rule
  5. effects of P and fluids on melting behavior

Petrology and chemistry:

  1. typical chemical variation diagrams (Harker, TAS, AFM) and their use in categorizing magma types
  2. magma series (alkaline, tholeiitic, calc-alkaline)
  3. effects of crystal fractionation on magma chemistry
  4. effects of incompatibility of selected elements on chemistry of melts generated by partial melting
  5. isotope systematics for the Rb-Sr, Nd-Sm, and O systems

Give a brief definition of the following terms:

  1. REE
  2. stable vs. radiogenic isotope
  3. incompatible element
  4. heat of fusion
  5. fractional crystallization
  6. assimilation
  7. mode
  8. equilibrium vs. fractional melting (handouts)

Example questions:

Most crustal rocks have more 87Sr than mantle rocks. Why?

Crater Lake (Mt. Mazama) is located in the Oregon Cascades. See Figs in Winter.

  1. What processes may have caused the variation in the chemistries of the volcanic rocks? Be specific in describing what causes the variation for each oxide.
  2. Based on the (incomplete) chemistry data available, classify these rocks as calc-alkaline or tholeiitic, and justify your classification.

Assume a mafic magma containing Ni and REE's is crystallizing olivine and plagioclase.

  1. What are the mineral formulae for olivine and plagioclase?
  2. What will happen to the concentration of Ni in the residual liquid, as the system crystallizes?
  3. What distinctive feature will the REE pattern of the residual liquid show, as the system crystallizes?

As you prepare by reviewing the text and your notes, think up similar questions.




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B. Saini-Eidukat
Geology 422/622