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Alaska Volcano Observatory
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Sample info : 11
Sample ID:11
Station ID:11
Latitude:51.9531
Longitude:178.5356
Datum:NAD83
Sample Type 1:Lava
Field Lithology:Dacite
Text Description:
High-silica dacite of the Double Point dacite. Color: brownish gray (5 YR 5/l). Texture: hypocrystalline, porphyritic with feldspar phenocrysts as much as 3 mm long. Zoned and twinned plagioclase, 25-30 percent, varies in composition from An35 to An45 and averages An40. Accessory minerals are euhedral orthopyroxene, 2 percent; snbhedral clinopyroxene, 2 percent; magnetite, 1 percent; and tridymite, 1 percent. The fluidal glassy to cryptocrystalline groundmass carries pyroxene, magnetite and plagioclase microlites. The plagioclase microlites have an average composition of An43.

References:
Geology of Little Sitkin Island, Alaska


Sample Location

URL: avo.alaska.edu/samples/sample_info.php
Page modified: August 7, 2013 07:43
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