Sample: 96-Mc-32B


Sample ID: 96-Mc-32B [1] [2]
Station ID: 96-Mc-32
AT Num:
Volcano: Akutan
Possible source:
Eruption:
Collector: McGimsey, R. G.
Date sampled: 1996-00-00
Sample type 1: Lava
Color: gray
Final unit: lea
Text Description: Qol- pre-glacial lavas (Pleistocene). Lava flows are exposed locally, mostly around base of present Akutan cone; elsewhere covered by Holocene tephra (Qtu). Flows are typically thick (>5 m) and tend to form prominent cliffs. Rocks are medium gray, dark gray, and olive gray porphyritic andesites (56.5-59.8% SiO2, loc. 10 and 11, table 11) containing phenocrysts of plagioclase (5-30%, 4-5 mm), clinopyroxene (1-7%, 3 mm), orthopyroxene (trace-4%, 1-5 mm), and olivine (0-1%, 2 mm) in cryptocrystalline to pilotaxitic groundmasses. Whole rock 40Ar/39Ar mean age of andesite is 0.36 +/-0.05 Ma.
Sample Location:

References Cited

[1] Geology of Akutan Island, Alaska, 1998

Richter, D. H., Waythomas, C. F., McGimsey, R. G., and Stelling, P. L., 1998, Geology of Akutan Island, Alaska: U.S. Geological Survey Open-File Report 98-0135, 22 p., 1 sheet, scale 1:48,000.

[2] The eruptive history, magmatic evolution, and influence of glacial ice at long-lived Akutan volcano, eastern Aleutian Islands, Alaska, 2020

Coombs, M.L., and Jicha, B.R., 2020, The eruptive history, magmatic evolution, and influence of glacial ice at long-lived Akutan volcano, eastern Aleutian Islands, Alaska: GSA Bulletin, 29 p., https://doi.org/10.1130/B35667.1.