| Text Description: |
Gray, medium-grained biotite quartz diorite with a color index of 16. Volume percentages are: zoned and unzoned andesine-oligoclase, 56; orthoclase, 7.2; quartz, 21; biotite, 8.0; hornblende, 3.6; clinopyroxene, 2.4; opaque oxide, 1.0; chlorite, 0.4; apatite, 0.3; sphene and epidote, trace. This rock, from the east shore of Bay of Waterfalls, is located near the edge of the largest pluton. Coarser and darker border phases with septa of recrystallized basaltic rocks occur just a few yards from this rock, but the main contact is underwater in Bay of Waterfalls. Characteristically, rocks this close to the border are more mafic than the main mass, and appear blotchy from irregular concentrations of dark minerals. |
full-text PDF 4.7 MB