Sample: 54-Sn-284B
| Sample ID: | 54-Sn-284B [1] | ||||||||||
| Station ID: | 54-Sn-284B | ||||||||||
| 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: | Granite, the matrix of a "plum pudding" rock, from a beach boulder near the head of the north arm of Skan Bay. The texture is hypidiomorphic-granular; the original rock contains many inclusions but this analysis is of matrix only. Felsic minerals compose 93-97 percent of the rock: 10-20 percent quartz, 50-70 percent alkalic feldspar heavily altered to kaolin (10-20 percent), and 15-25 percent plagioclase partly altered to epidote (0.1-0.5 percent), sericite (0.1-1 percent), and kaolin (lumped with above). The plagioclase composition, by extinction angle, is A18 [mean of 5 crystals, standard deviation is 9 percent An, average amount of zoning per individual plagioclase crystal is 0 Percent An per crystal]. Mafic minerals compose 3-7 percent: 2-3 percent hornblende and 0.1-0.5 percent is biotite both partly altered to epidote (0.1-1 percent) and penninite (0.1-0.3 percent), 1-1.5 percent is magnetite, 0.1-1 percent is sphene slightly altered to lucoxene, 0.1-0.5 percent is rutile occurring as stubby yellow rods in sphene, and 0.1-0.3 percent is penninite (interstitial). Comparison of the mode and norm for this rock indicates that the alkalic feldspar contains large quantities of both orthoclase and albite. | ||||||||||
| Sample Location: |
  Legend ✕
200 km 100 mi |
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