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NDSU Geosciences Petrology 422/622
Study Questions for Exam 2
Since the last exam, we have covered portions of Winter chapters 8-18 and kimberlites in Ch 19. 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
- 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.)
- crystallization and melting in ternary systems (example: the fo-en-di system)
- batch vs. fractional melting (handouts)
- the Gibbs phase rule
- effects of P and fluids on melting behavior
Petrology and chemistry:
- typical chemical variation diagrams (Harker, TAS, AFM) and their use in categorizing magma types
- magma series (alkaline, tholeiitic, calc-alkaline)
- effects of crystal fractionation on magma chemistry
- effects of incompatibility of selected elements on chemistry of melts generated by partial melting
- isotope systematics for the Rb-Sr, Nd-Sm, and O systems
Give a brief definition of the following terms:
- REE
- stable vs. radiogenic isotope
- incompatible element
- heat of fusion
- fractional crystallization
- assimilation
- mode
- 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.
- 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.
- 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.
- What are the mineral formulae for olivine and plagioclase?
- What will happen to the concentration of Ni in the residual liquid, as the system crystallizes?
- 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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