The white granite of the Idaho Batholith near Boise, Idaho, contains dark gray xenoliths
of metamorphic material. Which is older? How do you know?
A) Granite; the principle of superposition
B) Xenoliths; the principle of cross-cutting relations
C) Granite; the principle of unconformities
D) Xenoliths; the principle of inclusions
Why is quartz a bad mineral to use to determine a metamorphic environment?
A) Because it is not common in metamorphic rocks
B) Because silicate minerals do not metamorphose
C) Because quartz is stable over a wide range of metamorphic settings
D) Because it can only be used in hydrothermal metamorphism