Sample: 54-D-100
| Sample ID: | 54-D-100 [1] |
| Station ID: | 54-D-100 |
| AT Num: | |
| Volcano: | Makushin |
| Possible source: | |
| Eruption: | |
| Collector: | Drewes, Harald |
| Date sampled: | 1954-01-01 |
| Sample type 1: | Countryrock |
| Color: | |
| Final unit: | |
| Text Description: | Granodiorite from the Captains pluton 1 mile southwest of the head of Captains Bay. The texture is hypidiomorphic-granular to porphyritic. Felsic minerals compose 75-85 percent of the rock: 10-15 percent quartz, 13-17 percent orthoclase partly altered to kaolin (2-4 percent), and 50-55 percent plagioclase partially altered to sericite (0.5-1.5 percent) and clinozoisite (<0.01 percent). The plagioclase composition, by extinction angle, is An48 [mean of 24 crystals, standard deviation is 14 percent An, average amount of zoning per individual plagioclase crystal is 16 percent An per crystal], by index oils, is An44. Mafic minerals compose 15-25 percent: 1 percent pyroxene (all as small inclusions in one large plagioclase crystal), 12-15 percent hornblende (50 percent of this is massive and poikilitic with magnetite, 50 percent of this is uralitic fibers), 3-5 percent biotite partially altered to penninite (1-2 percent) and ilmenite and sphene (0.5-1.5 percent) which in turn are altered to leucoxene (<1 percent), 2.4 percent magnetite, and <1 percent apatite (in feldspar). |
| 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 75 PDF 6.7 MB
plate 76 PDF 113 KB
plate 77 PDF 250 KB
table 1 PDF 326 KB