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Sample: P49Se16

Sample ID: P49Se16 [1] [2]
Station ID: P49Se16
AT Num:
Volcano: Semisopochnoi
Possible source:
Eruption:
Collector: Powers, H. A.
Date sampled: 1949-05-01
Sample type 1: Lava
Color:
Final unit: Pochnoi volcanics
Text Description: Specimen P49Se16 is from the next to the lowest flow exposed on Tuman Head, (104,475' E., 3,450' N.). According to Powers, who collected this specimen, the section here, is largely pyroclastic and rich in bombs and scoria. The flow from which the specimen was collected ranges in thickness from 10 to 20 feet. The rock is dense medium-gray (N 5) olivine-hypersthene basalt, with seriate texture. The plagioclase, in crystals as much as 3 mm in size, averages An77, judging from the average refractive index. The olivine (Fa20) is in grains as much as one-half mm in diameter, and is pale yellowish green in hand specimen. The augite grains, which are as much as 1 mm in diameter, are yellowish green in thin section. Hypersthene prisms are much smaller, on the average. Magnetite and apatite are recognizable accessories.
Sample Location:

References Cited

[1] Geologic reconnaissance of Semisopochnoi Island, western Aleutian Islands, Alaska, 1959

Coats, R. R., 1959, Geologic reconnaissance of Semisopochnoi Island, western Aleutian Islands, Alaska: in Investigations of Alaskan volcanoes, U.S. Geological Survey Bulletin 1028-O, p. 477-519, 1 sheet, scale 1:25,000.
full-text PDF 1.4 MB
plate 59 PDF 2.7 MB

[2] Postglacial eruptive history and geochemistry of Semisopochnoi volcano, western Aleutian Islands, Alaska, 2018

Coombs, M.L., Larsen, J.F., and Neal, C.A., 2018, Postglacial eruptive history and geochemistry of Semisopochnoi volcano, western Aleutian Islands, Alaska: U.S. Geological Survey Scientific Investigations Report 2017-5150, 32 p., https://doi.org/10.3133/sir20175150.