A brief description of a low grade regionally metamorphosed
region in the Madoc area in Southern Ontario
is given. Plagioclase compositions from metamorphosed
basic rocks of this region were studied with the intention
of finding co-existing plagioclases in the region of
peristerite solvus. X-ray diffraction was found useful in determining the presence of two co-existing plagioclase feldspars. Two
peaks occurred in the region of the 131 and 131 peaks if
this was the case. Compositional determinations for
albitic feldspars were found inaccurate as the angular
separation (Δ29) between the 131 and 131 peaks was
apparently reduced indicating plagioclase composition less
than An0. For anorthite rich feldspars the angular
separation between 131 and 131 gave relatively accurate
compositions. The electron microprobe was used·to determine the plagioclase compositions of samples from the Madoc area.
Results compared well for anorthite rich feldspars determined
by both X-ray diffraction and. electron microprobe
techniques. Only one rock was found to contain two plgioclases related to a peristerite solvus. A zoned nature appears to exist. Albite and oligoclase coexist, the oligoclase grading into andesine. Also, albitic plagioclase is associated with epidote inclusions; a diffusion relationship probably existing between the two. With increased metamorphic grade, epidote disappears and the anorthite content of
plagioclase increases. / Thesis / Bachelor of Science (BSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/20686 |
| Date | 05 1900 |
| Creators | White, Michael |
| Contributors | Science |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
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