TEXTURAL AND MICROANALYSIS OF IGNEOUS ROCKS: TOOLS ...

3.5.2 CSDs as Guides for Microanalysis
I selected three samples from Site 1203 for detailed microanalysis of plagio-
clase phenocrysts based upon CSD curvature (Fig. 3.6). I chose to examine Site
1203 Units 14 and 31 due to the highly kinked nature of their CSDs. I also chose
one gently curved CSD sample, the top of Site 1203 Unit 3, for microanalysis to
compare with the results from the strongly kinked CSDs. I selected two large
phenocrysts, one each from the middle and bottom of Site 884 Unit 8 for micro-
analysis. I divided non-linear CSDs into two segments for targeted microanalysis
based upon the approximate position CSD slope change (Fig. 3.6a). A generaliza-
tion of the division of CSDs into separate segments, which are hereafter referred
to as Population A (smaller L) and Population B (larger L), is illustrated in fig-
ure 3.6a. The locations and sample names of each plagioclase crystal analyzed in
this study, as listed in tables 3.3 and 3.4, are labeled in figure 3.6b-e. The stereo-
logic correction used to convert 2D crystal sizes to 3D crystal sizes for generation
of true 3D CSD plots was applied to each crystal each crystal examined in order
to accurately sample CSD segments shown in figure 3.6b-e.
3.5.3 Petrography and Crystal Zoning Patterns of Microanalysis Samples
3.5.3.1 Site 1203 Unit 3
Unit 3 basalts have massive textures and large plagioclase phenocrysts (i.e.,
population B) that occur both as individual euhedral crystals and as portions of
rounded glomerocrysts (e.g., Fig. 3.7a). Both the large euhedral crystals and the
crystals present within glomerocrysts exhibit oscillatory zoning (e.g., Fig. 3.8d)
superimposed upn normal zonation ± distinct changes in An content of > 5 mole %
(e.g., Fig. 3.8c,d). Major element zonation is visible in backscatter electron images
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