Review Questions for Chapter 17:
Subduction-Related Igneous Activity, Part II: Continental Arcs.
1. Cite some reasons why crustal contamination is more evident in continental arcs than in island arcs.
2. Why is the subcontinental lithospheric mantle likely to differ significantly from the sub-oceanic
lithospheric mantle?
3. How would you expect 87Sr/86Sr to vary in magmas that traverse a significant thickness of ancient
continental crust? 143Nd/144Nd? Why? Why might the CVZ of the Andes show higher 87Sr/86Sr and
lower 143Nd/144Nd than the NVZ or SVZ?
4. Why might a low dip angle of subduction inhibit volcanism in a continental arc?
5. What are bimodal volcanic suites, and how do they probably form?
6. How do the major batholith belts relate to continental-arc volcanics? Why are the batholiths
exposed in some areas and covered by volcanics in others?
7. Describe the underplate remelting model for tonalites and explain why, if it is true, arc batholiths
may not strictly conform to intrusive equivalents of arc volcanics.
8. Why is a hydrous melt less likely to reach the surface as lava than an anhydrous melt? Use an
appropriate P-T phase diagram to illustrate.