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4310M2K_S10 - GLY4310 68 points 18 took exam Name Florida...

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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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