Sample: 54-Sn-198
| Sample ID: | 54-Sn-198 [1] |
| Station ID: | 54-Sn-198 |
| 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: | Granodiorite from the rock bench at the tip of the headland south of the largest stream on the north side of Skan Bay. The texture is hypidiomorphic-granular. The rock contains 70-75 percent felsic minerals: 7-10 percent quartz, 15-18 percent orthoclase partially altered to kaolin (1-3 percent), and 45-50 percent plagioclase preferentially altered in centers to sericite (3-5 percent). The plagioclase composition, by extinction angle, is An40 [mean of 35 crystals, standard deviation is 9 percent An, average amount of zoning per individual plagioclase crystal is 0 percent An per crystal]; by index oils, is An39. Mafic minerals make up 25-30 percent; 5-10 percent clinopyroxene slightly altered to hornblende 10.3-0.5 percent), 3.7 percent hornblende partially altered to antigorite (1-2 percent) and minor magnetite, 10-15 percent biotite slightly altered to penninite (<0.01 percent), 2-3 percent magnetite, <1 percent sphene slightly altered to leucoxene (<0.01 percent), and 0.5-1.5 percent apatite. |
| 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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plate 76 PDF 113 KB
plate 77 PDF 250 KB
table 1 PDF 326 KB