Igneous Rocks Lecture Notes

Igneous Rocks Lecture Notes - Petrology Review Rock: A...

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2 Petrology Review Rock: A naturally occurring consolidated material usually composed of grains of one or more minerals. ¾ Igneous Rocks: Rocks formed directly from the solidification of magma (or lava) ¾ Sedimentary Rocks: Rocks formed by the physical deposition and hardening (lithification) of loose rock, by chemical precipitation from solutions, or by secretions from animals ¾ Metamorphic Rocks: Rocks formed from pre-existing rocks that are changed mineralogically, texturally, or chemically in the solid state by pressure, temperature, and/or solutions.
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3 The Rock Cycle Rock Cycle: All rock types may form at the expense of another rock type if the original rock type is force out of equilibrium with its physical or chemical environment. Igneous rocks sediments (via weathering and erosion) Sediments sedimentary rock (via lithification) Sedimentary rocks Metamorphic rocks (via metamporphism) Metamorphic rocks Magma (via partial or complete melting) Magma Igneous rock (via crystallization)
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4 Igneous Rocks An igneous rock forms directly from the solidification of magma or lava ¾ Magma: molten rock that occurs inside the earth ¾ Lava: molten rock that occurs at or near the earth’s surface Intrusive (Plutonic) Igneous Rocks: rocks that crystallize beneath the earth’s surface (cool slowly (10 3 -10 6 years) – generally coarse grained) Extrusive (Volcanic) Igneous Rocks: rocks that crystallize on or near the earth’s surface (cool quickly) – generally fine- grained)
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5 Igneous Rock Classification Igneous rocks are classified using composition and texture. Composition: What is the chemical and mineralogical make-up of the rock? Texture: How is the rock put together? Grain size indicates the size of the crystals or grains in the rock: Coarse-grained : Big crystals (>1mm, from slow cooling) Fine-grained : (small crystals (<1mm, from fast cooling) There are 2 distinct (but complementary) classifications of igneous rock: The Chemical Classification The Field Classification
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6 The Chemical Classification of Igneous Rocks The chemical composition of a magma or lava determines which minerals form and
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Igneous Rocks Lecture Notes - Petrology Review Rock: A...

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