Earth Sciences 1022A/B Lecture Notes - Lecture 3: Igneous Differentiation, Pyroxene, Amphibole
10 Jan 2017
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Document Summary
Igneous rocks are crystalized from molten silicate material called magma that forms at high temperatures and pressures deep in the earth. Magma rises through the crust and either reaches the surface by volcanoes (extrusive) or cools below surface (intrusive) According to bowen"s reaction series, discontinuous (different molecular structures of olivine, pyroxene, amphibole, biotite), and continuous (same plagioclase structure) Magma composition can also change through assimilation (piecies of host rock fall into the magma and melt) and magma mixing where one body of magma invades another producing a composition intermediate between two. Rock composition from dark (less silica) to light (more silica) minerals. Igneous rock textures includes size, shape, and arrangement of crystals: aphanitic. Formed by rapid cooling at or near the ground"s surface. Formed by slow cooling below the surface. Does not make it to ground surface: porphyritic. Has larger crystals surrounded by smaller ones: glassy.
