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TYPES OF ROCKS Tectonics and Metamorphism Regional metamorphism Zone of burial metamorphism Granitic magma rises and causes contact metamorphism Figure 10.13 © 2008, John Wiley and Sons, Inc. Blueschist and eclogite metamorphism What’s metamorphism? The set of changes that occur in rocks as a result of elevated temperatures and pressures. It takes place in solid state, without melting. Where does it occur? Underground, very deep but specially where there are stress forces Factors in metamorphism? Temperature and pressure. Types of metamorphism Figure 10.2 © 2008, John Wiley and Sons, Inc. Metamorphism is a complex process including: •Loss of water •Orientation of minerals. •Recrystallization. •New minerals formation. Second process: orientation. Extreme pressure produces foliation, a planar arrangement of mineral grains giving a layered texture. (Esquistosidad) See animation: http://www.bioygeo.info/Animaciones/Foliation1.swf Third process: recrystallization. Increasing the size of some minerals. Shale Sedimentary Rock © 2008, John Wiley and Sons, Inc. Slate Fine grained, low grade metamorphic rock with slaty cleavage. Phyllite Fine grained, high grade metamorphic rock with foliation. From shale to gneiss Figure 10.3 Diagenesis Shale Low-Grade Slate Medium-Grade Phyllite * Sillmanite and Kyanite Al2O3 with different crystal structures © 2008, John Wiley and Sons, Inc. High-Grade Gneiss There are some metamorphic rocks without foliation. Why? If the previous rock hasn’t got planar components foliation is impossible Sandstone Dominantly quartz minerals Quartzite Very little foliation due to low diversity of minerals. Video sobre recristalización: http://www.youtube.com/watch?v=J_2FdkRqmCA&feature=related Quarzite and marble are metamorphic rocks without foliation Made of cacite Made of quartz From limestones From sandstones Soft, it reacts with acid Hard, it doesn’t react A collection of metamorphic rocks