Sample: 54-B-12
| Sample ID: | 54-B-12 [1] |
| Station ID: | 54-B-12 |
| AT Num: | |
| Volcano: | Makushin |
| Possible source: | |
| Eruption: | |
| Collector: | Barnett, H. F. J. |
| Date sampled: | 1954-01-01 |
| Sample type 1: | Lava |
| Color: | |
| Final unit: | |
| Text Description: | feldspathic basalt porphyry from a dike in the Unalaska formation near Summer Bay in Unalaska Bay. It is dark bluish gray and contains phenocrysts as large as 1 millimeter. Phenocrysts compose 10 percent of the rock: 9 percent calcic labradorite, which forms embayed crystals, euhedral laths, and grains with inconspicuous normal zoning ; 1 percent augite (?) , which forms altered euhedra and is replaced by penninite(?) ; and a trace of pyrite. The groundmass has a felty texture and consists of abundant euhedral and subhedral laths of calcic andesine and scattered granules of a black opaque mineral. Alteration is moderate, producing disseminated calcite and penninite and traces of uralite and chlorite. |
| Sample Location: |
References Cited
[1] Geology of Unalaska Island and adjacent insular shelf, Aleutian Islands, Alaska, 1961
Drewes, Harald, Fraser, G. D., Snyder, G. L., and Barnett, H. F. Jr., 1961, Geology of Unalaska Island and adjacent insular shelf, Aleutian Islands, Alaska: in Investigations of Alaskan volcanoes, U.S. Geological Survey Bulletin 1028-S, p. 583-676, 3 sheets, scale 2 at 1:250,000 and 1 unknown.
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table 1 PDF 326 KB