TEXTURAL AND MICROANALYSIS OF IGNEOUS ROCKS: TOOLS ...

and Rb (Fig. 4.11d,e).
4.4.3.3 Yttrium and the Rare Earth Elements La, Ce, Pr, Nd, Sm, and Eu
The highest Y abundances were measured in Unit 4 crystal cores and inter-
mediate zones (Fig. 4.12b). There is no other obvious systematic variation in Y
abundance between phenocryst zones in crystals from either Unit. At a given An
content, Unit 10 phenocrysts have greater La, Ce, Pr, Nd, Sm, and Eu. Where core
and interior sections of Unit 4 phenocrysts overlap, they tend to have lower overall
REE abundances relative to the instances where there is no overlap (Fig. 4.12).
The opposite relationship holds true or Unit 10 phenocryst zones with overlap-
ping An, where core and intermediate zones tend to have greater REE abundances
(Fig. 4.12).
4.4.4 Sr Isotope Microdrilling
There are subtle variations in 87 Sr/ 86 SrI between crystals zones in Unit 4 and
10 crystals (Figs. 4.13, 4.8, 4.9, and 4.10; Table 4.3). Unit 4 crystals have much
less radiogenic 87 Sr/ 86 SrI than Unit 10 crystals (Fig. 4.13). The rim of Unit 4
crystal D bears the most radiogenic 87 Sr/ 86 SrI observed in a Unit 4 crystal and
exhibits a higher 87 Sr/ 86 SrI than all Site 1137 upper group whole-rock samples
reported by Ingle et al. [75] (Fig. 4.8b). The rim zone of crystal D is bounded by a
resorption surface and a change from An67 in the intermediate zone to An64 at the
rim. All other Unit 4 plagioclase zones overlap Site 1137 upper group whole-rock
87 Sr/ 86 SrI reported by Ingle et al. [75]. There is little other distinction in terms
of 87 Sr/ 86 SrI between core, intermediate, and rim zones (Fig. 4.13).
Site 1137 lower group whole-rock samples reported by Ingle et al. [75] extend
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