426P S09 Exam 1 - - 1 - Name:...

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Unformatted text preview: - 1 - Name: _____________________________________ *************************************************************************************************** GEO 426P Igneous and Metamorphic Petrology Exam 1 20 February 2009 50 MINUTES FOR 25 QUESTIONS , EACH WORTH 4 POINTS , FOR 100 POINTS TOTAL N O BOOKS OR NOTES ; C ALCULATOR OK BUT PROBABLY NOT NEEDED I NDICATE YOUR RESPONSE BY CIRCLING ZERO , ONE , OR MORE LETTERS TO THE LEFT OF ANY CORRECT ANSWERS . *************************************************************************************************** 1. What is the optic sign of a mineral with n = 1.530, n = 1.650, and n = 1.685? a. positive b. negative c. can't tell without more information 2. Consider the sections listed below through a biaxial indicatrix. Which if any of them would yield a Bxo figure for a positive mineral? a. X-Y section b. Y-Z section c. X-Z section d. circular section e. random section 3. Consider a crystal in a thin section oriented to produce retardation that is equal to 1.5 wavelengths for light of a particularly frequency. At the analyzer, light of this frequency will experience: a. total transmission b. total extinction c. partial extinction and partial transmission 4. Consider the sections through a biaxial indicatrix listed below. Circle the letter(s) for any or all of them that can be found by searching orthoscopically for grains with distinctive birefringence. a. X-Y section b. Y-Z section c. X-Z section d. circular section e. random section - 2 - 5. The interference figure shown below was obtained from a biaxial negative mineral. At the point in the northeast quadrant marked by the dot, the vibration directions are NW-SE and NE-SW; what are their indices of refraction? NW-SE: NE-SW: a. n a. n b. n ' b. n ' c. n c. n d. n ' d. n ' e. n e. n *************************************************************************************************** 6. Which of the following lists presents the features in order of increasing depth in the Earth? a. bottom of oceanic crust; olivine-spinel transition; "low-velocity layer"; transition from Si(tetrahedral) to Si(octahedral) coordination b. olivine-spinel transition; bottom of oceanic crust; transition from Si(tetrahedral) to Si(octahedral) coordination; "low-velocity layer" c. "low-velocity layer"; bottom of oceanic crust; olivine-spinel transition; transition from Si(tetrahedral) to Si(octahedral) coordination d. olivine-spinel transition; bottom of oceanic crust; transition from Si(tetrahedral) to Si(octahedral) coordination; "low-velocity layer" e. bottom of oceanic crust; "low-velocity layer"; olivine-spinel transition; transition from Si(tetrahedral) to Si(octahedral) coordination...
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This note was uploaded on 02/21/2010 for the course GEO 420k taught by Professor Staff during the Spring '08 term at University of Texas at Austin.

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426P S09 Exam 1 - - 1 - Name:...

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