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.