Geol 2312 – Petrology
Quiz 3
Spring 2016
Name_____________________
Chapters 8 & 9
Score _____/15
1) Circle the 6 elements that are considered major and minor elements in a whole rock
composition (1.5 pts)
Na
U
P
Mg
Al
Si
La
Ni
Zr
Zr
Fe
2) Name an element that would be classified as an incompatible trace element. (0.5 pt)
3) In converting weight % of elemental oxides of chemical analysis to atomic %, what other
parameter must we know? Circle the correct answer (0.5 pts)
a. Density of minerals
b. Molecular weights of the elemental oxides
c. Mineral mode
d. Mineral compositions
4) Identify the volcanic rock type (basalt, andesite, rhyolite,or phonolite) that would have the
following chemical characteristics. (2 pts)
a. A mafic composition with relative high concentrations of MgO and CaO compared to other
rocks basalt
b. Has highest SiO2 concentrations, typically greater than 70% rhyolite
c. Moderate SiO2 (~55-60%), high Al2O3 (15-20%), and relatively high concentrations of K2O
and Na2O (>10% combined) phonolite
d. Similar to c, but modest of K2O and Na2O (<7% combined) andesite
5) CIPW norm calculations estimate the idealized mineralogy of a rock from it whole rock
composition. Match the CIPW phase (or phases) that is(are) the major carrier(s) of these
elements (2 pts)
a. K - or
ap – apatite
b. P - ap
il – ilmenite
c. Na - ab
or – orthoclase
d. Ti - il
di – diopside
e. Ca - an
ab – albite
f. Al – an, ab, or
an – anorthite
6) Which iron oxide species FeO or Fe2O3…
a. Is preferred at higher states of oxygen fugacity? Fe2O3
b. Is composed of ferric iron (Fe+3)? Fe2O3
(1pt)
F
7) On the AFM diagram to the right: (2.5 pts)
a. Label the AFM corners
b. Label the Tholeiitic and Calc-Alkaline Fields
c. What chemical components do
A F M stand for?
A- Na+K - alkalis
F- Fe, FeO+Fe2O3
M- Mg, MgO
d. Which data points are from
Volcanic Arc settings Purple or Red?
A
Tholeiitic
Calc-Alkaline
M
8) The formula for the partition coefficient of a trace element in an igneous system is given by:
KD = CS/CL. What do the S and the L stand for? S- solid L- liquid (0.5 pts)
9) Does an incompatible trace element have a KD, greater or less than one? ____________(0.5
pts)
10) Circle the trace element that would be expected to become depleted in a mafic magma that is
fractional crystallizing a dunite (Ol) (0.5 pts)
Ni
Zr
Rb
Ba
Rare Earth Elements (excl. Eu)
11) During partial melting of the mantle, does low (5%) or high (30%) degrees of melting (<5%)
promote magmas enriched in incompatible trace elements? _______________ (0.5%)
12) In the Rare Earth Element normalization diagram:
a.
(2 pts)
Label the light rare earth (LREE) and heavy
rare earth (HREE) sides of the diagram
b. What are the REE normalized to? Chondritic
meteorites
c. This pattern is from a basalt that was
generated by fractional crystallization of a
gabbro (Pl+Ol+Cpx+Ox). What mineral in
that assemblage likely caused the depletion of
Europium (Eu) relative to the other REEs?
Plagioclase
Light REE
Heavy REE
d. Which REEs are more incompatible with these 4 mineral phases, La-Ce-Nd or Er-Yb-Lu?
Circle one group.
13) In the normalization multielement diagram
(1 pt)
a. Which side of the diagram has elements that are
more strongly incompatible? Right or Left?
b. What Rock/Chondrite values would elements like
Ni and Cr have on this diagram? <1
Use in Midterm.
14) The REE normalization diagrams below show REE pattern generated from partial melting two
different mantle compositions that differ in the Al-bearing phase (Pl in shallow mantle, garnet in
deep mantle).
60%Ol 15%Opx 15%Cpx 10%Plag
57% Ol
14% Opx
14% Cpx 14% Grt
10
8.
sample/chondrite
sample/chondrite
10.
6.
4.
2.
8.
6.
4.
2
0.
La Ce Nd Sm Eu
Tb
Er
Yb Lu
0.
5 La Ce
5
Nd
6 Sm
6 Eu 6Tb
6 Er 6 Yb 7
7