TEXTURAL AND MICROANALYSIS OF IGNEOUS ROCKS: TOOLS ...

Unit 31 > Site 884 Unit 8 (Table 3.3). Selected trace element ratios are shown
plotted against An content in figure 3.11. It is difficult to estimate the amount
of error introduced to the inverted compositions via the choice of partition coeffi-
cients, and for this reason the error shown in figure 3.11 is analytical uncertainty
only. Parent magma Ba/Sr ratios of population A and B crystals from Unit 3
overlap at An > 70 and trend to higher ratios at An contents approaching An60
(Fig. 3.11a). Parent magmas of Unit 14 and 31 population A crystals trend to
higher Ba/Sr than parent magmas of population B crystals (Fig. 3.11a). Par-
ent magma Ba/Sr of population B crystals from Units 14, 31, and Site 884 Unit
8 overlap and are lower than Unit 3 population B parent magmas (Fig. 3.11a).
Population A crystals from Units 14 and 31 trend to the lowest overall La/Sm
ratios, but there are no other noteworthy La/Sm distinctions between Units or
crystal populations (Fig. 3.11b). Samarium was below analytical detection limits
in the Site 884 Unit 8 crystals. In terms of La/Y ratios, parent magmas from
populations A and B from Units 3, 14, and 31 overlap, but population A parent
magmas exhibit a wider range of La/Y (Fig. 3.13). I measured trace elements in
a single Unit 31 population A crystal, which has lower parent magma La/Y than
the population B crystals (Fig. 3.13). When the range of La/Y in parent magmas
of the Unit 3 and 14 population A magmas are considered, the separation of the
single Unit 31 population A crystal parent magma from parent magmas of the
population B crystals is probably an artifact of limited sampling. In summary,
the parent magmas of population B crystals from Unit 31 and Site 884 Unit 8 are
the most LREE and trace element depleted of all crystals sampled. There appears
to be little significant fractionation of REE between parent magmas of population
A and B crystals, but there are distinct differences in Ba and Sr content.
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