ENVS 1050 Chapter 5: Geology Notes - week 5
12 Feb 2016
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Originate from partial melting of the peridotite a dark coloured igneous rock that is the main constituent of the upper mantle. Can be generated from subduction zones but when it migrates upward, the pressure diminishes and reduces the melting temperature. It will crystallize as the dense magma collects beneath the crustal rocks. Are found in or adjacent of the continental margins. Result is the more silicate rich magma of intermediate composition or andessitic composition * Magma of intermediate composition can evolve from magic magma by the process of magmatic differentiation. The changed magma are termed as secondary magmas as felsic rocks are found in too much of a large quantity. Oxygen and silicon are the most abundant in the rocks. They form two groups: dark: are rich in magnesium and low in silica - olivine, pyrozene, amphibole and biotitte light: greater amounts of potassium sodium and calcium they are rich in silica - quarts, feldspars and muscovite.
