4_Igneous Rocks - Making magma magma vs. lava phase diagram...

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Unformatted text preview: Making magma magma vs. lava phase diagram Cooling magma, crystallization texture differentiation Classification of igneous rocks Extrusive processes and landforms mafic (basalt): flood basalts, pillows, volcanoes intermediate to felsic: volcanoes and calderas Dikes and sills Chapter 5: Igneous Rocks Next lecture: Finish chapter 5, then chapter 7 Where does the magma that feeds volcanoes come from? (A) isolated chambers of magma in the crust and mantle; (B) a universal pool of magma in the completely molten mantle; (C) the liquid core of the earth; (D) all of the above. Question Phase Diagram increase temperature decrease pressure add water (See Figure 5-20) x How can we melt a rock at point x ? s o l i d u s The phase diagram describes the state of a material, such as a rock body, given its temperature and pressure. Phase transitions also depend on the minerals in the rock, and the presence of fluids in the pore spaces. Making magma magma vs. lava phase diagram Cooling magma, crystallization texture differentiation Classification of igneous rocks Extrusive processes and landforms mafic (basalt): flood basalts, pillows, volcanoes intermediate to felsic: volcanoes and calderas Dikes and sills Chapter 5: Igneous Rocks Next lecture: Finish chapter 5, then chapter 7 (Figure 5-4) obsidian http://volcanoes.usgs.gov/ disorganized atomic structure Cooling Magma texture : sizes, shapes, and arrangement of mineral grains (crystals) What does texture tell us about cooling history? WHERE? HOW FAST? TEXTURE below the surface cooled slowly large crystals cooled quickly quenched above the surface small crystals above the surface, under water no crystals (glass) Fe-Mg-rich magma Some types of igneous differentiation Fe-Mg-depleted magma 1. Mafic minerals (such as olivine) form... 2. causing remaining magma to become more Fe-Mg-poor (depleted) 3. Mafic minerals settle to bottom of magma chamber Some rock deep in the crust 1. Rock body is heated enough to partially melt. 2. Felsic material is first to melt; rock left behind becomes more mafic 3. Melt rises to shallower levels. Making magma magma vs. lava phase diagram Cooling magma, crystallization texture differentiation Classification of igneous rocks Extrusive processes and landforms mafic (basalt): flood basalts, pillows, volcanoes intermediate to felsic: volcanoes and calderas Dikes and sills Chapter 5: Igneous Rocks Next lecture: Finish chapter 5, then chapter 7 Igneous Rock Classification (simplified)...
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4_Igneous Rocks - Making magma magma vs. lava phase diagram...

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