1. Lecture 4 Igneous Rocks, Intrusive Activity and the Origin of Igneous Rocks

2. Lecture Outline IRock Types IIDefinitions IIIIgneous Rocks A)Extrusive v Intrusive B)Textures i.Intrusive Textures ii.Extrusive Textures iii.Porphyritic Texture C)Composition IVMagma A)Chemistry i.Felsic ii.Intermediate iii.Mafic iv.Ultramafic B)Formation of Magma C)Magmatic Variability i.Bowen's Reaction Series ii.Fractionation VPlate Tectonics and Igneous Rocks A)Divergent Boundary B)Convergent Boundary C)Hot Spot VIIntrusive Bodies Physical Geology

3. Rock Types What is the basis for this classification? Physical Geology

4. Definitions magma - molten rock that is produced from pre-existing rock in the asthenosphere by Earth's internal heat. The magma then rises into the lithosphere and cools on the surface or in the subsurface. lava-magma flowing on the surface of the Earth igneous-formed from fire plutonic-formed at depth Physical Geology

5. Igneous Rocks Physical Geology

6. Igneous Rocks Intrusive Rocks Extrusive Rocks Physical Geology

7. Igneous Rocks Intrusive Textures PhaneriticPegmatitic Physical Geology

8. Igneous Rocks Extrusive Textures AphaniticGlassy Vesicular Fragmental Physical Geology

9. Igneous Rocks Porphyritic Texture Physical Geology

10. Igneous Rocks Composition Major Elements Oxide % by Weight SiO 2 35.0-80.0 Al 2 O 3 8.0-22.0 TiO 2 Fe 2 O 3 FeO 4.0- MnO 30.0 MgO CaO Na 2 O 1.5-8.0 K 2 O 0.5-8.0 H 2 O +,- varies P 2 O 5 <0.15 CO 2 varies } Minor (Trace) Elements Li, Be, Sc, V, Cr, Co, Ni, Cu, Zn Ga,Rb, Sr, Y, Zr, Nb, Ba, Pb, F, Cl, S Rare Earth Elements Physical Geology

11. Magma Physical Geology

12. Felsic Magma silica content -high, >65% temperature-< 900 0 C viscosity-high Na, K, Al content-high Ca, Fe, Mg content-very low eruption-explosive (Mount St. Helens) minerals-Na-rich plagioclase feldspar potassium feldspar quartz Physical Geology

13. Intermediate Magma silica content -intermediate, 53 - 65% temperature-900 - 1100 0 C viscosity-intermediate Na, K, Al content-intermediate Ca, Fe, Mg content-intermediate eruption-intermediate (Andes Mtns.) minerals-plagioclase feldspar amphibole Physical Geology

14. Mafic Magma silica content -low, 45 - 52% temperature-1100 - 1300 0 C viscosity-low (fluid) Na, K, Al content-low Ca, Fe, Mg content-high eruption-quiet (Kilauea) minerals-Ca-rich plagioclase feldspar pyroxene olivine Physical Geology

15. Ultramafic Magma silica content -very low, <45% temperature-~1400 0 C viscosity-very low (fluid) Na, K, Al content-very low Ca, Fe, Mg content-very high eruption-none (Cyprus) minerals-pyroxene olivine Physical Geology

16. Igneous Rocks Magma Formation Processes Decompression Melting Addition of Impurities Temperature (Geothermal Gradient) Physical Geology

17. Magma Formation The Geothermal Gradient Physical Geology

18. Magma Formation Impurities Physical Geology

19. Magmatic Variability Bowen's Reaction Series Physical Geology

20. Magmatic Variability Fractionation Differentiation/Partial Melting Assimilation Mixing Physical Geology

21. Magmatic Variability Differentiation Physical Geology

22. Magmatic Variability Assimilation Physical Geology

23. Magmatic Variability Magma Mixing Physical Geology

24. Plate Tectonics and Igneous Rocks Physical Geology

25. Plate Tectonics and Igneous Rocks Divergent Boundary Physical Geology

26. Plate Tectonics and Igneous Rocks Convergent Boundary Physical Geology

27. Plate Tectonics and Igneous Rocks Hot Spots Physical Geology

28. Intrusive Bodies Physical Geology

29. Shallow Intrusive Bodies Volcanic Neck Ship Rock, NM Physical Geology

30. Shallow Intrusive Bodies Sill Dike Physical Geology

31. Deep Intrusive Bodies Batholith Stock Diapir Physical Geology