1. Physical conditions & Bowen’s Reaction Series (Fo then Fa) (Ens then Aug & Di) (An) (Ab) Mafic Felsic

2. Igneous Rocks & Bowen’s Reaction Series Mafic Felsic

3. Composition of Igneous Rocks

4. Heat Sources in the Earth 1. Heat from the early accretion and differentiation of the Earth u still slowly reaching surface 2. Heat released by the radioactive breakdown of unstable nuclides

5. Preference for mineral phase Preference for melt Plot of ionic radius vs. ionic charge for trace elements of geological interest. Ionic radii are quoted for eight-fold coordination to allow for comparison between elements. From Rollinson (1993). Ionic charge vs. radius

6. Heat flow and geothermal gradients 10°C/km 16°/km 24°C/km

7. Heat flow and geothermal gradients 10°C/km 16°/km 24°C/km Base of crustal root in the Sierra ~30km (=300°C), in the Basin & Range ~20km (=480°C)

8. Estimating pressure increases Figure 1-9. Estimated ranges of oceanic and continental steady-state geotherms to a depth of 100 km using upper and lower limits based on heat flows measured near the surface. After Sclater et al. (1980), Earth. Rev. Geophys. Space Sci., 18, 269-311. Estimate ~3.33 kbar/km (1 GPa = 10 kbar) ~6 kb ~12 kb

9. zTzT k = q (q) k, thermal conductivity constant (medium- dependent) To calculate A geothermal gradient from heat flow: