TYPES OF ROCKS

Tectonics and Metamorphism Regional metamorphism Zone of burial metamorphism Granitic magma rises and causes contact metamorphism Blueschist and eclogite metamorphism Figure 10.13 © 2008, John Wiley and Sons, Inc.

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.

Underground, very deep but specially where there are stress forces Where does it occur? Squeeze 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 Slate Phyllite Sedimentary Rock Fine grained, low grade metamorphic rock with slaty cleavage. Fine grained, high grade metamorphic rock with foliation. © 2008, John Wiley and Sons, Inc.

From shale to gneiss Figure 10.3 Diagenesis Low-Grade Medium-Grade Slate Medium-Grade Phyllite * Sillmanite and Kyanite Al2O3 with different crystal structures High-Grade © 2008, John Wiley and Sons, Inc. Gneiss

There are some metamorphic rocks without foliation. Why?

If the previous rock hasn’t got planar components foliation is impossible Sandstone Quartzite Very little foliation due to low diversity of minerals. Dominantly quartz 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