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Geology- Igneous Rocks 2
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- 1Classification of magma/ Igneous RocksComposition(mineral Content) =
Chemical composition- % of silica
Mineral composition- 99% of igneous rocks are made of silicates. Bowen's reaction series - 2Bowen's Reaction Series
- 3Variation in Igneous rock types Why?Different sources of magma, magmatic differentiation, contamination
- 4Generation of Melt- HeatMost Igneous rocks will melt between 700-1200 degrees at the earth's surface. Pressure and temperature increase with depth.(30 degrees for 1km), melting occors in places of high heat e.g Hot spots.
- 5Generation of Melt- PressureMelting does not normally occur due to pressure, occurs due to decompression as magma rises pressure falls.
- 6Generation of melt- Flux MeltingWater acts as a flux, causes rocks to melt at lower temperatures.
- 7Fractional CrystallizationAs magma cools the minerals crystallise out according to their crystallization/melting points. this means that some minerals crystallize out first and if they are denser sink to the bottom of the magma causing the magma to become depleted. In theory process is called magmatic differentiation.
- 8Magmatic DifferentiationOnly occurs when the melting of magma is very slow, so that the early formed crystals can sink to the bottom of the magma. The edges of the melt cool rapidly so is closest to the original composition of the magma.
- 9Hypothetical magma chamber
- 10Why does Magmatic Differentiation occur?Due to different minerals crystallizing out at different temperatures, though a process called Fractional crystallization.
- 11Movement of magmaRises due to pressure (convection currents), will not rise if it is not under pressure.
- 12Movement of magma: Doming
- 13Movement of magma: Stoping
- 14Movement of Magma: Subduction
- 15Movement of magma: Extension
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- Fichas sobre Geology- Igneous Rocks 2, creado por holliebishop1996 el 05/03/2014.
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- holliebishop1996
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