1. Chapter 4 Magma, Igneous Rocks and Intrusive Activity

2. Igneous Rocks - Lava

3. Igneous Rocks - Magma

4. Igneous Rocks
Magma
Intrusive/Plutonic
Lava
Extrusive/Volcanic

5. Components of Magma/Lava
Liquid portion = melt
Solids = silicate mineral crystals
Volatiles/Gases
water vapor (H2O)
carbon dioxide (CO2)
sulfur dioxide (SO2)

6. Crystalization of Magma
Texture
Appearance
Size/arrangement of minerals

7. Factors affecting crystal size
Rate of cooling
SiO2
Dissolved gases

9. Igneous Rock Textures

13. Glassy

14. Pyroclastic

15. Pegmatitic

16. Vesicular

17. Igneous Compositions Mostly Silicates
Light
Non-ferromagnesian/Felsic
Quartz
Feldspars
Muscovite

18. Igneous Compositions Mostly Silicates
Dark
Ferromagnesian/Mafic
Olivine
Pyroxene
Amphibole
Biotite

19. Igneous Compositions Mostly Silicates
Intermediate
Andesitic
Dark & light minerals
Violent eruptions

20. Igneous Compositions Mostly Silicates
Ultramafic
Very dark
Rare

21. Silica & Magma Behavior
High silica content
Granitic
Continental
High viscosity
Violent

22. Silica & Magma Behavior
Low silica content
Basaltic
Oceanic
Low viscosity
Mild

23. Origin of Magma Heat Temperature increases with depth
Geothermal Gradient
~ 20oC to 30oC per kilometer

24. Origin of Magma Pressure & Heat

25. Origin of Magma decompression melting

26. Origin of Magma water reduces melting point

27. Evolution of Magmas Bowen’s Reaction Series
Minerals crystallize via melting points
The magma composition always changes

28. Bowen’s Reaction Series
Figure 4.23

29. End of Chapter 4