Sample: Snyder_1959_4

Sample ID:	Snyder_1959_4 ^[1]
Station ID:	Snyder_1959_4
AT Num:
Volcano:	Little Sitkin
Possible source:
Eruption:
Collector:	Snyder, G. L.
Date sampled:
Sample type 1:	Lava
Color:	medium light gray
Final unit:
Text Description:	Andesite of Williwaw Cove formation. Color: medium light gray (N 6). Texture: holocrystalline, porphyritic with both feldspar and pyroxene phenocrysts as much as 4 mm long. Plagioclase, 45-60 percent, ranges in composition from An45 to An60 and averages An51; complex oscillatory zoning and graphic fritting common within individual plagioclase grains. Subhedral clinopyroxene, 10 percent; euhedral orthopyroxene, 10 percent; and anhedral olivine, 1 percent, characterized by brown stains on some fractures. Anhedral magnetite, 5 percent, particularly abundant. Groundmass consists of mesh of feldspar and pyroxene microlites and magnetite dust. Groundmass plagioclase averages An43.
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