HTML University

Science Dept.

Geology and Soils GEO 100 Notes
Igneous Rocks

1. Definitions
   1. Rock: An aggregate of one or more minerals

   2. Igneous Rock: Congealed from a hot silicate melt

   3. Magma: Hot silicate melt, intrusive

   4. Lava: Hot silicate melt, extrusive

   5. Texture: Size of crystals, if any

   6. Cooling History: As shown by texture

2. Element Abundance O, Si, Al, Fe, Ca, Na, K, Mg

3. Classification of Igneous Rocks
   1. Texture : Related to Cooling history - Physical

   2. Mineralogy : Related to Chemical History

4. Texture Terms
   1. Glassy

   2. Fine - Aphanitic

   3. Coarse - Phaneritic

   4. Porphyritic - Different Sizes
      1. Porphyritic - less than 25% phenocrysts
      2. Porphyry more - than 25% phenocrysts

   5. Pegmatitic

   6. Vesicular

   7. Pyroclastic - Tuff

5. Mineralogy
   1. Minerals of the Igneous Rocks
      1. Olivine
      2. Pyroxenes (eg. Augite)
      3. Amphiboles (eg. Hornblende)
      4. Ca - Na Feldspars (eg. Labradorite)
      5. Na - Ca Feldspars (eg. Andesine)
      6. K Feldspar (eg. Orthoclase, Microcline)
      7. Micas (eg. Muscovite, Biotite)
      8. Quartz

   2. Bowens Reaction Series

6. Palisades Sill Plutonic Intrusion
   1. Minerals :
      1. Olivine
      2. Pyroxene (eg. Augite)
      3. Ca - Na Feldspar
      4. Amphiboles (eg. Hornblende)
      5. Na - Ca Feldspar
      6. Biotite
      7. K Feldspar
      8. Quartz

   2. Magmatic Differentiation via Gravitational Setting of Crystals

7. Granitic.....Intermediate.....Mafic.....Ultramafic
   "Acidic"............................"Basic"

8. Link to the Igneous Rock Identification Chart