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6.2 Igneous Rocks. Igneous Rock Formation. Igneous rocks are classified as: Felsic – Thick and slow moving magma. Contains Silica, Ca, Fe and Mg Forms light colored quartz and orthoclase feldspar. Igneous Rock Formation. Igneous rocks are classified as:
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Igneous Rock Formation Igneous rocks are classified as: Felsic – Thick and slow moving magma. • Contains Silica, Ca, Fe and Mg • Forms light colored quartz and orthoclase feldspar
Igneous Rock Formation Igneous rocks are classified as: Mafic: Formed from hotter, thinner and more fluid. • Contains large amounts of Fe, Mg and low amounts of silica. • Forms darker rocks.
Igneous Rock Formation Underground Magma • Forms Intrusive Rocks • Cools slowly • Has coarse surfaces • Produces larger crystals within the rock.
Igneous Rock Formation Magma Above the Surface (Lava) • Forms Extrusive Rocks • Cools Quickly • Forms Microscopic/no crystals • May form porphyry (large crystals surrounded by fine grained rock)
Igneous Rock Formation Igneous Rock Description • Granite Family • Felsic • Coarse (Intrusive) • Makes up most of the continental crust • Only visible after upward expansion. • Other examples: Pumice and Obsidian
Igneous Rock Formation Igneous Rock Description • Gabbro • Darker • Dense
Igneous Rock Formation Igneous Rock Description • Diorite Family • Grays and greens • Coarse Grained
Igneous Rock Formation Igneous Intrusion • What is an igneous intrusion? A rock mass that cools inside the Earth’s interior (Pluton). • These include: • Dikes – Vertically cooled igneous rock • Sills – Horizontally cooled igneous rock (b/t rock layers)
Igneous Rock Formation Igneous Intrusions Batholiths • Largest plutons • Made of granite or granordiorite • The cores of many mountain ranges • Exposed through upward expansion Laccoliths • Magma that bulges upwards into domes