TEXTURAL AND MICROANALYSIS OF IGNEOUS ROCKS: TOOLS ...

3.5.5 Trace Elements
3.5.5.1 Measured Compositions
Trace element abundances measured by LA-ICP-MS in plagioclase crystals
from each Unit are reported in table 3.3 and illustrated in figure 3.10. Yttrium,
Sr, La, Nd, Sm, and Eu abundance exhibit little or no correlation with An content
in figure 3.10. More prominent negative correlations of Ba and Ce abundance with
An content are apparent if figures 3.10c,e, although these correlations appear to be
most significant at An contents < An70. In the An80−87 range, which is dominated
by the interiors of population B crystals from each Unit, Unit 14 population B
crystals trend to highest Sr abundance, Unit 31 crystals have the lowest Sr of the
three Site 1203 Units I examined, and the Site 884 Unit 8 crystals have lower
abundances Sr than all Site 1203 crystals (Fig. 3.10). In terms of Y, Sm, Nd, and
Eu all crystals in the An80−87 range overlap. It should be noted, however, that the
Site 884 Unit 8 crystals tend to have the lowest abundances of these elements and
Sm low enough to be below analytical detection limits. Lanthanum and Ce exhibit
similar patterns in crystal zones in the An80−87 range, where Unit 31 crystals are
the most La and Ce depleted of the Site 1203 samples and the Site 884 Unit 8
crystals have notably lower La and Ce abundances (Fig. 3.10d,e)
3.5.5.2 Inferred Parent Magma Compositions
I inverted the compositions of magmas in equilibrium with the crystals at dif-
ferent periods during their growth. The calculated parent magma compositions
and the partition coefficients used for inversion are listed in table 3.4. Rare earth
element, Ti, Ba, and Sr abundance in parent magmas of the four Units I examined
exhibit the following general trend of decreasing abundance: Unit 3 ≅ Unit 14 >
116