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TYPES OF ROCKS
© 2008, John Wiley and Sons, Inc.
Tectonics and Metamorphism
Figure 10.13
Zone of burial metamorphism
Blueschist and eclogite metamorphism
Regional metamorphism
Granitic magma rises and causes contact 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.
© 2008, John Wiley and Sons, Inc.Figure 10.2
Types of metamorphism
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.
© 2008, John Wiley and Sons, Inc.
Shale Slate Phyllite
SedimentaryRock
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
Shale
Slate
Phyllite
Gneiss
Diagenesis
Low-Grade
Medium-Grade
High-Grade
* Sillmanite and KyaniteAl2O3 with different
crystal structures
There are some metamorphic rocks without foliation. Why?
If the previous rock hasn’t got planar components foliation is impossible
Sandstone Quartzite
Dominantly quartz minerals 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
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