March 4th - March 4th Igneous Textures 6) Vesicles: trapped...

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March 4 th Igneous Textures 6) Vesicles: trapped gas bubbles… ‘vesicular texture’ 7) Amygdules: vesicles filled in with minerals- origin of agate… ‘amygdaloidal  texture’ 2) Kinds Of Igneous Rocks Aphanitic Rhyolite Andesite Basalt Volcanic/Extrusive Phaneritic Granite Diorite Gabbro Plutonic/Intrusive  SiO 2  Viscosity  Light                       Dark  Fe, Mg   Explosiveness Igneous Rock Names: Usually texture + compositional name - Phaneritic granite = light colored - Pegmatic diorite = medium gray or green gray - Vesicular aphanitic basalt = dark colored 3) Plutonism a) Geometries and sizes - Magmas may not make it to the surface - This happens because: * Encounter cooler rocks * Don’t carry much extra heat * Always near crystallization temperature ~ Can happen near surface or 10’s of km below surface - Creates ‘intrusive (plutonic) igneous rocks
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This note was uploaded on 04/30/2008 for the course GEOL 120 taught by Professor Maglouihlin during the Spring '08 term at Colorado State.

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March 4th - March 4th Igneous Textures 6) Vesicles: trapped...

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