4310M2K_S10 - GLY4310 68 points 18 took exam Name March 24,...

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1 GLY4310 Name 68 points March 24, 2010 18 took exam Florida Atlantic University PETROLOGY -- MIDTERM TWO 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) 2 F 1. The seismic Moho and the petrologic Moho are the same depth below the surface. 5 T 2. Heavy isotopes like those of strontium or neodymium are not likely to mass fractionate significantly during either partial melting or fractional crystallization. 3 T 3. If a melt is fluid saturated, any increase in volatile content will produce one or more additional phases. 3 T 4. The dry peridotite solidus has a positive P/T slope. Thus, lowering the pressure at constant T would eventually produce melting. 7 F 5. Fast-spreading ridges have a pronounced axial valley, 30 to 50 kilometers in width, and 1-5 kilometers in depth. Inward facing fault scarps are seen, a feature shared with continental rift zones. An inner rift valley is often present, 3-9 kilometers in width, with a flat floor. This is the definition of a slow-spreading ridge. 2 F 6. Heat-flow at slow-spreading ridges is much higher than at fast-spreading ridges. 8 F 7. Carbon dioxide solubility is very high in silicate melts. Just the opposite 3 T 8. At a given depth of melting, fractional crystallization is simply the reverse of partial melting. 3 F 9. The first crystals formed in a magma are more likely to be anhedral than crystals formed later in the crystallization 5 F 10. Basaltic magma generally contains more water than granitic magmas. 5 T 11. The olivine in the upper gabbro layers of a Gabbro Ophiolite complex is richer in fayalite than the olivine in the peridotite layer. 6 T 12. Augite is a higher temperature mineral in Bowen’s Reaction Series than hornblende. 4 T 13. Tholeiites are far more voluminous than alkaline rocks.
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2 5 F 14. Ultramafic rocks like those in the mantle ordinarily contain volatiles 1 T 15. Garnet, spinel, and plagioclase lherzolites all have the same composition, but melting will not begin at the same temperature, since garnet, spinel, and plagioclase all have different melting points. 4 T 16. LIL and HFS data for N-MORB and OIB show that the K/Ba and Zr/Nb ratios are much higher for the N-MORB's than for OIB, suggesting at least two separate mantle reservoirs. 9 F 17. Basaltic magmas have much higher volatile contents, on average, than granitic magmas. Granites are wet, basalts dry. 1 F 18. In terms of total rock volume, stratovolcanoes like those in the Cascades are much larger than the shield volcanoes of Hawaii. 2 T 19. The following reaction is an example of a discontinuous reaction. 4 T 20. If P f = P total , the melt is saturated with volatiles. 8 T 21. Rocks form an alkaline magma series may be found within both continental and oceanic plates, but are only associated with convergent plate margins.
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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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4310M2K_S10 - GLY4310 68 points 18 took exam Name March 24,...

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