| Text Description: |
Granodiorite. The rocks 1,500 yards south of Blind Cove have a color index near 10 and are more felsic than most of the granodiorite. These rocks contain a few dark rounded fine-grained patches as much as severa1 centimeters in diameter that appear to be recrystallized and partly assimilated wall rock. A marked preferred orientation of biotite and hornblende was noted in some outcrops. A peculiar texture, suggestive of mortar structure, is visible in thin section. This texture consists of large (3 mm) zoned plagioclase crystals with narrow interstitial bands of granular quartz (0.4 mm) and orthoclase (0.2 mm). The quartz and orthoclase crystallized later than the plagioclase; possibly magma motion helped to produce the texture. A modal analysis of one of these rocks (specimen no. 2) gives the following volume percentages: zoned andesine-oligoclase, 57; orthoclase, 11; quartz, 21; biotite, 4.7; hornblende, 4.5 (some of these in blocky crystals with a maximum diameter of 8 mm); opaque oxides, 0.9; chlorite (mostly after biotite), 0.8; sphene, apatite, and zircon, total, 0.1. |
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