Sample: 53-B-13
| Sample ID: | 53-B-13 [1] |
| Station ID: | 53-B-13 |
| AT Num: | |
| Volcano: | Makushin |
| Possible source: | |
| Eruption: | |
| Collector: | Barnett, H. F. J. |
| Date sampled: | 1953-01-01 |
| Sample type 1: | Countryrock |
| Color: | |
| Final unit: | |
| Text Description: | Granogabbro occurring one-third mile from the Beaver pluton contact on the east side of Final Bay. The texture is hypidiomorphic and the groundmass is myrmekitic. Felsic minerals compose 80-85 percent of the rock: 7-10 percent quartz, 15-25 percent alkali feldspar partially altered to kaolin (2-3 percent), and 50-58 percent plagioclase partly altered to sericite (about 5 percent) and epidote-clinozoisite (about 1 percent). The plagioclase composition, by extinction angle, is A62 [mean of 28 crystals, standard deviation is 10 percent An, average amount of zoning per individual plagioclase crystal is 2 percent An per crystal], by index oils, is An54. Mafic minerals compose 15-20 percent: 10-13 percent uralitic hornblende (probably 85 percent of this after pyroxene, 15 percent after biotite) partly altered to penninite (0.5-1.5 percent). 0.5-1.5 percent sphene partly altered to leucoxene (0.1 percent), 4-6 percent magnetite, and <1 percent apatite. The discrepancy in plagioclase composition is probably due to sodium in the alkalic feldspar, and potassium in the plagioclase (?). |
| 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.
full-text PDF 3.3 MB
plate 75 PDF 6.7 MB
plate 76 PDF 113 KB
plate 77 PDF 250 KB
table 1 PDF 326 KB