Geo HW 3

Geo HW 3 - Geology 2341 A Term 2008 Worcester Polytechnic...

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Geology 2341, A Term 2008 Worcester Polytechnic Institute Homework Assignment 3, Due at 5:00 PM Sep. 9 The crust is enriched in oxygen, silicon, alumnium, potassium and sodium. The mantle is enriched in iron, calciuim and magnesium. The oceanic crust has a composition intermediate between the continental crust and the mantle. The most common minerals in the crust are silicates -- combinations of oxygen, silicon, and (usually) other positively charged ions. The Mineral Gallery offers a full text search ability which you will use to complete this exercise. Critical Concepts : 1. Solid Solutions : Most minerals do not have a fixed chemical composition (quartz is a notable exception). Plagioclase feldspars are a mineral group in which composition varies between two extremes (albite is the sodium-rich end member and anorthite is the calcium-rich end member). Plagioclase is concentrated in igneous rocks from the oceanic crust . Alkali feldspars are members of a solid solution series between a potassium-rich end
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Geo HW 3 - Geology 2341 A Term 2008 Worcester Polytechnic...

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