TEXTURAL AND MICROANALYSIS OF IGNEOUS ROCKS: TOOLS ...

3.5.4 Major Elements
Major element compositions measured by EPMA and Ti abundances measured
by LA-ICP-MS in plagioclase crystals from each Unit are reported in table 3.3
and illustrated in figure 3.9.
3.5.4.1 Site 1203 Unit 3
I noted variations in An content apparent in backscatter electron images that
correlate with zoning patterns. Unit 3 Population A crystal cores fall into two
groups in terms of An content. The higher An group (An74−79) overlaps the
population B cores (An78−81) (Fig. 3.9a). The cores of population B crystals
extend to higher An contents (up to An81) than population A crystals. There is
no obvious variation in Mg # (measured in plagioclase) between population A
and B crystals or with An content.
3.5.4.2 Site 1203 Unit 14
The cores of population A crystals from Unit 14 also fall into two groups in
terms of An content. The more An rich population A group have An77−82 cores
that overlap the compositions of population B cores, and the lower An population
A group have An64−76 cores. The cores of population B crystals have a higher
range of An content (An81−87), but a single population B crystal with a core
composition of An73−74 was observed. There is no obvious variation in Mg #
(Mg/Mg+total Fe measured in plagioclase) between population A and B crystals
or with An content, but a single Unit 14 crystal rim (An56) has the lowest overall
Mg # (Fig. 3.9d).
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