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Sample: Snyder_1959_10

Sample ID: Snyder_1959_10 [1]
Station ID: Snyder_1959_10
AT Num:
Volcano: Little Sitkin
Possible source:
Eruption:
Collector: Snyder, G. L.
Date sampled:
Sample type 1: Lava
Color: medium dark gray
Final unit:
Text Description: High-silica dacite of Double Point dacite. Color: medium dark gray (N 4). Texture: hypocrystalline, porphyritic with blocky feldspar phenocrysts with maximum diameter of 5 mm. Eleven sections of the plagioclase, 25-30 percent, perpendicular to both albite twinning and basal cleavage give anorthite contents that appear to be distributed evenly from An23 to A55; complex zones and intergrowths common; groundmass microlites may group around An17 but cannot be determined accurately; two-fluid inclusions from 0.004-0.02 mm in diameter occupy negative crystals in certain zones of the feldspar. Stubby euhedral hypersthene, 5-10 percent, is pleochroic in light pink and light green. Accessories are clinopyroxene, 1 percent; magnetite, 2 percent; oxyhornblende, 1 percent; and tridymite, 1 percent. Fluidal groundmass glass has N=1.504(?).
Sample Location:

References Cited

[1] Geology of Little Sitkin Island, Alaska, 1959

Snyder, G. L., 1959, Geology of Little Sitkin Island, Alaska: in Investigations of Alaskan volcanoes, U.S. Geological Survey Bulletin 1028-H, p. 169-210, 1 plate, scale 1:20,000.