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A2 Igneous Rocks (Silicate Mineral Chemistry (Silicic (Mafic (Biotite,…
A2 Igneous Rocks
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Hot Spot Magma
Mantle plumes remain stationary, while plates move over them
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Origin of mantle plumes unclear, but high Fe content suggests origin from between mantle and core
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Solidification of Magma
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Crystal-melt separation in 2 ways- (1) squeezed out by filter pressing, (2) gravity settling of Olivine crystals
Palisades Sill, 300m thick Dolerite, fine grained chilled margins, olivine rich layer, olivine decreases further up
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Contamination of Magma
Composition changed as magma melts, reacts or incorporates surrounding rocks= Xenoliths
2 different contaminations- (1) meting of contaminate due to conduction, then mixes with magma, (2) chemical reaction or incorporation of Xenoliths not melting
Contamination of magma results from stoping, which occurs when dense and fractured blocks fall into body of buoyant magma
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Formation of Acid Magma
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Collapse of U Mantle (peels away from crust and sinks) (Slab Detachment), results in contact between CC and Asthenosphere. Causes melting within CC
Delamination of root, transfer of heat from Asthenosphere into CC
Pressure
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Effect of water
Complicated if water is present, water lowers melting temp, causes flux melting, greater pressure= more water= lower melting temp
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