Igneous Processes and Intrusive Bodies

 

Terms to learn:

magma                                Bowen's Reaction Series      aphanitic
partial melting                assimilation                                  phaneritic
magma mixing                 porphyritic                                    pyroclastic
pegmatitic                          vesicular                                        intrusive (plutonic)
extrusive (volcanic)      mafic                                                 felsic

 

Topic outline:

1. Magma
2. Igneous processes
   1. Magma evolution
      1. Differentiation
         1. Bowen’s reaction series - discontinuous branch – continuous branch
         2. Crystal settling
      2. Partial melting
      3. Assimilation
      4. Magma mixing
3. Plate tectonic occurrence of igneous rocks
   1. Divergent boundaries – basalt
   2. Intraplate activity
   3. Convergent boundaries – andesite, granite
4. Igneous rock – intrusive vs. extrusive
5. Igneous rock identification
   1. texture
   2. mineral composition – mafic, felsic, intermediate, ultramafic
   3. volcanic/plutonic equivalents

 

When you are finished with this topic, you should be able to answer these questions:

1. How can color and size of mineral grains in igneous rock give clues about the composition and cooling history of a magma?
2. Distinguish between the two major kinds of igneous rock.
3. In what ways can the composition of magma be changed?
4. What does a porphyritic texture indicate about the formation of an igneous rock?
5. Describe the differences between the continuous and discontinuous branches of Bowen's reaction series.