JEG100H1 Chapter Notes - Chapter 10: Porphyritic, Weathered, Aphanite
16 Oct 2016
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Document Summary
Less dense magma rises to surface, cools and solidifies. Gravity moves loose material downslope, transported by erosional agents, sediments deposited. Compacted by weight of overlying material, percolating water fills pores with mineral material. Metamorphic rock created by great pressure and heat. Cycle restarts when rock melts and becomes magma again. Igneous and metamorphic formed by internal heat, sedimentary formed by external processes. Magma made of silicate ions, gas, water vapor, mineral crystals. Dark silicates are rich in iron, magnesium, poor in silica. Light silicates are rich in silica, potassium, sodium, calcium. Coarse-grained texture: large masses of magma crystallize at great depths. Porphyritic texture: large crystals embedded in smaller crystals. Vesicular texture: spherical voids left by gas bubbles. Glassy texture: rapid cooling, ions solidify in no particular order. Pyroclastic/fragmented texture: consolidation of smaller individual rock fragments. Magmatic differentiation: formation of secondary magma from parent. Ions selectively removed from magma as crystals form, crystals settle to bottom.
