ES 4971-4973 Petrology
Homework 13
Project Skills and Sediments
Name ____________________
A. Project skills: Protolith Determinations
1.
You examine multiple fields of view in a thin section of a leucocratic
rock from the Losee Metamorphic Suite. In total you get 70 quartz, 80
Plagioclase or sericitized Plagioclase, 4 Potassium feldspars, 14
Almandine Garnet and 24 mafic minerals. Calculate a multiplier for, and
tabulate the percents of, Quartz, K-spars, and Plagioclases, then plot your
sample on the graph below.
2.
For a metasediment in Table 8 of Volkert and Drake, convert the
Major-oxide wt% concentrations into atom% for sample 299.
3.
From the atom % column for the previous problem, column 7, use the
values for Si, Al, Ca, Na and K and calculate
a. Si/(Si + Al) = __________________
b. Ca + Na/ (Ca + Na + K) = ________________
c. Now plot sample 299 on this chart:
B. Sedimentary Petrology
4. A well rounded, well sorted sand of > 90% quartz is a quartz arenite. You
expect it
a. near the source area in the Highlands
b. at the beach and nearshore
5. An angular, poorly sorted sand of > 25% feldspar is an arkose. You
expect it
a. near the source area in the Highlands.
b. at the beach and nearshore
6. Which of these detrital grain size classifications is a log scale?
a. Udden – Wentworth
b. Phi
7. In the detrital rock classification of Dott (1964) a Wacke has
a. between 15 to 75% mud matrix.
b. less than 15% mud matrix.
8. Define Micrite and Spar
9. What is similar in the carbonate classifications of Kendall versus Embry
and Klovan?
10. Explain why flat clays settle more slowly than a rounded particle of the
same mass on density.
11. Which is the more mature sediment?
a. a well sorted, rounded quartz sand
b. an angular graywacke with several volcanic minerals
12. Explain the difference between matrix and cement in terms of timing.
13. Name two main phases of diagenesis.
14. What source produces Quartz that does NOT have undulose extinction?
15. Why are quartz overgrowths optically continuous with the original
quartz grain?
16. Under what circumstances does calcite grow and silicates dissolve?
a. acidic
b. alkaline
c. neutral pH
17. Define litharenite
18. What is Sericite? What does it commonly replace?
19. Explain the chemical differences between calcite and dolomite; gypsum
and anhydrite.
20. Define Allochem, Ooid
21.Explain how you would recognize a Brachiopod in thin section.