Sample: Snyder_1959_3

Sample ID:	Snyder_1959_3 ^[1]
Station ID:	Snyder_1959_3
AT Num:
Volcano:	Little Sitkin
Possible source:
Eruption:
Collector:	Snyder, G. L.
Date sampled:
Sample type 1:	Lava
Color:	medium gray
Final unit:
Text Description:	Andesite of Little Sitkin dacite. Color: medium gray (N 5). Texture: hypocrystalline, porphyritic with feldspar phenocrysts as much as 4 mm in diameter, and pyroxene phenocrysts as much as 3 mm long. Plagioclase megaphenocrysts, 20-30 percent, range from An35 to An56 and average An47; complex zoning and twinning common. Clinopyroxene, 8 percent, contains rare centers of orthopyroxene, 1 percent. Both unreacted olivine, 5 percent, and pyroxene are stained amber along joints. Magnetite, 2 percent, as anhedrons. Average composition of feldspar microlites in trachytic groundmass is An42.
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.

full-text PDF 2 MB

plate 23 PDF 7 MB