Quiz #3 -- Processes and Concepts of Geology
September 8, 2003

1. Please explain fractional crystallization of a magma, or how a basaltic magma can eventually yield in part a granite.

Early-formed crystals can produce a rock of primarily basaltic or gabbroic composition; the liquid can be drawn off through various processes and produce a more silica-rich rock upon further cooling; through this fractional crystallization, we can produce a granite through removal of the last remaining liquid; if there was no fractional crystallization, the resulting rock would have the same composition as the original magma, in this case basaltic.

2. What is the difference between a gabbro and a basalt? What are the most common minerals in each?

Gabbro is the intrusive (plutonic) or phaneritic equivalent of basalt. Both contain large amounts of Ca-plagioclase, pyroxene and olivine.

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Bonus Questions: Always optional. One point for each correct answer.

Mahmoud Abbas resigned this weekend as Prime Minister of what? The Palestinian Authority
Name one candidate for the Democratic Party 2004 presidential nomination: Edwards, Dean, Lieberman, Sharpton, etc.