4310M1K_S10 - GLY4310 52 points 18 took exam Name February...

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1 GLY4310 Name 52 points February 8, 2010 18 took exam Florida Atlantic University PETROLOGY -- MIDTERM ONE KEY True-False - Print the letter T or F in the blank to indicate if each of the following statements is true or false. Illegible answers are wrong. (1 point each) 4 F 1. A biotite-hornblende granite contains more biotite than hornblende. 3 F 2. In the IUGS classification scheme, the letter F refers to feldspars, including alkali and plagioclase. 8 T 3. If a rock is found in the middle of the QAP part of the IUGS diagram, it is silica excessive. 2 T 4. If a rock has P + M > 90%, it should be classified using the “gabbroic” diagram. 2 T 5. Rocks with an aphanitic texture are composed of either glass, or crystals too small to be seen with the unaided eye, or a mixture of these two. 0 F 6. During nucleation, the surface area/volume ratio is low. 1 T 7. In a magma chamber lacking magma movement, the rate of diffusion controls the rate of dissipation of the heat of crystallization. 1 F 8. Systems in which the cooling rate is rapid usually maintain equilibrium. 9 T 9. As they travel deeper in the mantle, the velocity of both P and S waves increases. 9 F 10. Pyrophyllite is a dioctahedral triphormic phyllosilicate. There are two layers in the structure, one tetrahedral, and one octahedral. Multiple-Choice - Choose the best response to each statement or question. Print the letter corresponding to your choice in the blank. (1 point each) 8 B 1. Large crystals formed by relatively slow cooling of magma below the earth’s surface are called: A. Phaneritic B. Phenocrysts C. Pyroclasts D. Xenocrysts
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2 9 C 2. In a chemical classification of igneous rocks, a rock with 48 wt % silica would be: A. Felsic B. Intermediate C. Mafic D. Ultramafic 4 C 3. A rock with 45% dark minerals would have which color classification? A. Leucocratic B. Melanocratic C. Mesotype D. Poikilitic 7 D 4. In the IUGS chemical classification scheme, what two variables are plotted? A. Wt % silica, Wt % alumina B. Wt % calcium, Wt % alumina C. Wt % alkali (Na 2 O + K 2 O), Wt % alumina D. Wt % alkali (Na 2 O + K 2 O), Wt % silica 7 A 5. In the IUGS classification scheme for pyroclastic rocks based on fragment size, tuff is composed mainly of what sized fragments? A. < 2 mm B. 2 - 64 mm C. > 64 mm D. Both B and C 1 C 6. Igneous minerals which form during solidification due to interactions between crystals and melt are said to be: A. Equant B. Phenocrysts C. Primary D. Secondary 8 C 7. A rock is composed of predominantly subhedral crystals. The rock texture may be described as: A. Equant B. Idiomorphic C. Hypidomorphic D. Xenomorphic 1 A 8. The most common metal on earth is: A. Aluminum B. Calcium C. Iron D. Titanium
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This note was uploaded on 12/13/2010 for the course GLY 4200c taught by Professor Warburton during the Spring '10 term at FAU.

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4310M1K_S10 - GLY4310 52 points 18 took exam Name February...

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