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SAMPLE INFO : 12
Sample ID:12
Station ID:12
Latitude:51.9531
Longitude:178.5356
Datum:NAD83
Sample Type 1:Lava
Field Lithology:Dacite
Text Description:
Rhyodacite of Pratt Point member of Little Sitkin dacite. Color: yellowish gray (5 P 7/1) to medium light gray (N 6). Texture: hypocrystalline, vesicular with "hairy" pumice developed locally, porphyritic with hornblende phenocrysts as much as 7 mm long and feldspar phenocrysts as much as 4 mm long. Plagioclase, 15-20 percent, ranges in composition from An27 to An50 and averages An40; sometimes poikilitic with inclusions of hornblende. Accessory minerals: oxyhornblende, 3-4 percent; hypersthene, 2-3 percent; quartz, 2-3 percent; magnetite, 1 percent. The quartz is characterized by conchoidal fractures and is very susceptible to plucking during grinding. The groundmass is about half small bubbles and half clear pinkish glass (N=1.490). The few plagioclase microlites average An39( ?).

References:
Geology of Little Sitkin Island, Alaska

GEOCHEM DATA
StationIDLatitudeLongitudeGeologistDateVisitedVolcanoEruptionLocation DescriptionText DescriptionSample IDMaterialSiO2TiO2Al2O3FeOTMnOMgOCaONa2OK2OP2O5Total-majorsREF majorsMETH majorsFe2O3/Fe203T origFeO/FeOT origVolatiles csvMETH volatilesCsRbBaSrLaCePrNdSmEuGdTbDyHoErTmYbLuYZrNbHfTaPbThUScVCrFeCoNiCuZnGaMoAsNaKRef trace1METH trace1RbBaSrLaCeNdSmEuGdDyErYbLuYZrNbPbThUScTiVCrNiCuZnGaRef trace2METH trace2Light csvHalogen csvother major csvother lile csvother ree csvother hfse csvother hpe csvother tm csvother misc csv
1251.9531178.5356Snyder, G. L.Little SitkinPratt Point member of Little Sitkin dacite from central part of mapped area about 0.9 mile south of East PointRhyodacite of Pratt Point member of Little Sitkin dacite. Color: yellowish gray (5 P 7/1) to medium light gray (N 6). Texture: hypocrystalline, vesicular with "hairy" pumice developed locally, porphyritic with hornblende phenocrysts as much as 7 mm long and feldspar phenocrysts as much as 4 mm long. Plagioclase, 15-20 percent, ranges in composition from An27 to An50 and averages An40; sometimes poikilitic with inclusions of hornblende. Accessory minerals: oxyhornblende, 3-4 percent; hypersthene, 2-3 percent; quartz, 2-3 percent; magnetite, 1 percent. The quartz is characterized by conchoidal fractures and is very susceptible to plucking during grinding. The groundmass is about half small bubbles and half clear pinkish glass (N=1.490). The few plagioclase microlites average An39( ?).12Whole Rock 68.99 0.38 15 3.65 0.12 1.15 3.45 4.3 2.06 0.11 99.86424NN1.522.27H2OM=0.08; H2OP=0.64; CO2=0.01NN 45.1 245 5.9 745XRFK V=1.7, M=NN, R=745;

SAMPLE LOCATION

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Page modified: July 14, 2014 13:37
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