TEXTURAL AND MICROANALYSIS OF IGNEOUS ROCKS: TOOLS ...

3.5.3.3 Site 1203 Unit 31
The Unit 31 basalt I examined has a massive texture and population B crys-
tals that occur as rounded and euhedral individual crystals or glomerocrysts (e.g.,
Fig. 3.7c). Most population B crystals exhibit interior oscillatory zoning superim-
posed upon normal zonation with distinct changes in An content near the rims,
often a > 10 mole % An change (e.g., Fig. 3.8j). A small number of population B
crystals exhibit patchy disorganized major element zoning in their interiors with
An variations close to the limits of An content resolution (∼ 1-2 mol % An) of
backscatter electron images (see Fig. 3.8i). Population A crystals are unzoned and
normal zoned (Fig. 3.8k,l). The single Unit 31 basalt sample I examined has 18%
modal abundance of plagioclase. I did not measure olivine modal abundances in
the Unit 31 sample but was estimated to be < 1% by Tarduno et al. [128].
3.5.3.4 Site 884 Unit 8
The Site 884 Unit 8 basalts I examined have massive textures and and cm size
population B crystals that occur as rounded clusters of crystals and individual
euhedral or rounded crystals (e.g., Fig. 3.7d,e). The interiors of the population B
crystals exhibit oscillatory type zoning and normal zonation with subtle decreases
in An content of 1-4 mole % near the rims (e.g., Fig. 3.8m,n). Thin (5-10 µm)
low An rims are apparent in backscatter electron images of population B crystals
but were not sampled in detail. The basalt sample from the middle of this flow
has 36% modal plagioclase abundance, the sample from the bottom of the flow
has 27% modal plagioclase abundance, and the sample from the flow top has 17%
modal plagioclase abundance. I did not measure olivine modal abundances in the
Site 884 Unit 8 samples but they were estimated to be < 1% by Rea et al. [118].
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