Arcs & continents. Updates/questions. Wednesday review, midterm on April 2nd Topics: Systematics for: Arcs Some continental rocks. Trace Elements: REEs. Enriched. Depleted. Figure 14-2. After Wilson (1989) Igneous Petrogenesis. Kluwer. MORB-normalized Spider Diagrams.
Figure 14-2. After Wilson (1989) Igneous Petrogenesis. Kluwer.
Figure 14-3. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall. Data from Sun and McDonough (1989).
Figure 9-13. After Wilson (1989). Igneous Petrogenesis. Unwin Hyman/Kluwer.
Ctl Crust (enriched) = hi 87Sr/86Sr, lo 143Nd/144Nd
by alpha decay
half life 106 Ga
Figure 13-12. Data from Ito et al. (1987) Chemical Geology, 62, 157-176; and LeRoex et al. (1983) J. Petrol., 24, 267-318.
Range in compositions = mantle array
Every composition by mixing end-members:
EM 1&2 -
HIMU - high m
238U -> 206Pb
So high 206Pb/204Pb
EM and HIMU from crustal sources (subducted OC + CC seds)
Figure 14-10. Nomenclature from Zindler and Hart (1986). After Wilson (1989) and Rollinson (1993).
Volcanism in arc-shaped region of volcanoes
Composition more diverse and silicic
Basalt generally occurs in subordinate quantities
Also more explosive than the quiescent basalts
Strato-volcanoes are the most common volcanic landform
Result of subduction: H2O melting
NOAA Ocean Explorer