ES 4971-4973 Petrology
Homework 8 Ch 9
Name _____________________
1. What is an incompatible element? Give an example.
2. Explain why Zirconium (symbol Zr) is more abundant when silica
SiO2 is relatively more abundant.
3. Look at Table 9.1. Which mineral will take more Rb, Sr, and Ba as it
crystallizes?
a. Olivines
b. Amphiboles
4. Example: For a hypothetical Basalt = 15% olivine, 25%
orthopyroxene, 25% clinopyroxene, and 35% plagioclase (all by
weight), using the data in Table 9-1, the bulk distribution coefficient
DRb for Rubidium Rb is:
DRb = (0.15 · 0.010) + (0.25 · 0.022) + (0.25 · 0.031) + (0.35 · 0.071)
Question: What is DSr for Strontium Sr?
5. Compatible elements have partition coefficients D much less than 1,
and incompatible elements have partition coefficients D much more
than 1.
a. True
b. False
6. At high temperatures, incompatible trace elements concentrate in the
a. liquid
b. solid
7. (Slide 20) If Orthoclase crystals begin to precipitate, but Plagioclase
does not precipitate, the ratio of Ba/Sr will decrease in the melt,
because more Barium than Strontium goes into the Orthoclase.
crystals.
a. True
b. False
8. For the following
F =0.25 DRb =0.045 DSr = 0.838
a.Calculate CL/CO for Rb
b. Calculate CL/CO for Sr
c. calculate the ratio Rb/Sr
9. A lab reports 48ppm Yttrium (Y) and 303ppm Chromium (Cr) from a
metabasalt in the Grenvillian “Byram Intrusive Suite” near Sparta NJ.
Consult figure 9.8b to determine the tectonic setting of the basalt.
a. an island arc
b. a mid-ocean ridge