Earth Sciences 1022A/B Lecture Notes - Lecture 2: Igneous Textures, Magma Chamber, Igneous Differentiation
14 Jan 2016
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Week 2 igneous rocks -- sept. 22nd, 2015. Igneous rocks (fire): crystalize 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). Igneous rocks are popular for interior decoration: granite. How magmas evolve: according to bowen"s reaction series. He became to world expert on igneous rocks. Through bowen"s reactions series in which crystals settle in a magma chamber. Earlier dark crystals remove heavy elements, leaving melt with lighter ones (magmatic differentiation) Discontinuous series: different molecular structures of olivine (single tetrahedra), pyroxene, the structures of the minerals (single chains), amphibole (double chains), biotite (sheets) Continuous series (plagioclase structure: ranges from sodium and calcium. Repeated crystal settling in a magma chamber results in the melt crystalizing through a series of minerals according to their decreasing melting temperatures.
