Sample: 54-Sn-284A
| Sample ID: | 54-Sn-284A [1] |
| Station ID: | 54-Sn-284A |
| AT Num: | |
| Volcano: | Makushin |
| Possible source: | |
| Eruption: | |
| Collector: | Snyder, G. L. |
| Date sampled: | 1954-01-01 |
| Sample type 1: | Countryrock |
| Color: | |
| Final unit: | |
| Text Description: | Recrystallized wallrock, equivalent to syenodiorite in composition, from a beach boulder at the southeast end of the north arm of Skan Bay: it occurs as an inclusion in granite. The texture is hypidiomorphic-granular. Felsic minerals compose 76-80 percent of the rock: 2-3 percent quartz, 5-10 percent orthoclase partially altered to kaolin (1-2 percent), and 65-70 percent plagioclase partially altered to sericite (2-3 percent) and clinozoisite (0.1 percent). The plagioclase composition, by extinction angle, is An35 (mean of 10 crystals, standard deviation is 6 percent An, average amount of zoning per individual plagioclase crystal is 11 percent An per crystal). Mafic minerals compose 20-25 percent: 10-14 percent hornblende (much is interstitial), 5-10 percent biotite partially altered to epidote (0.1-0.5 percent) and penninite (0.1-1 percent), 1-3 percent magnetite, 0.1-1 percent sphene (associated with the magnetite) partially altered to leucoxene (0.1-0.5 percent), one large grain of tourmaline (about 0.3 percent), and <0.01 percent hematite. |
| 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