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SAMPLE INFO : Snyder_1959_13
Sample ID:Snyder_1959_13
Station ID:Snyder_1959_13
Latitude:51.9531
Longitude:178.5356
Datum:NAD83
Sample Type 1:Lava
Field Lithology:Dacite
Text Description:
Rhyodacite lava from Pratt Point member of Little Sitkin dacite. Color: yellowish gray (5 P 7/1). Texture: hypocrystalline, vesicular, porphyritic with plagioclase phenocrysts as much as 5 mm and hornblende phenocrysts as much as 3 mm long. Plagioclase megaphenocrysts, 15-20 percent, are complexly zoned from cores of An55-60 to rims of An35-45; several feldspars poikilitic with small hornblende inclusions, 0.09 by 0.2 mm; minute clinopyroxene rods, 0.01 by 0.05 mm; and two-fluid inclusions in cavities with a maximum diameter of 0.04 mm. Hornblende, 36 percent, is pleochroic in shades of olive green, reddish brown, and black; several crystals have deeper pleochroism at borders than at center. Hypersthene, 1-2 percent, is the only pyroxene megaphenocryst; two crystals have a core of oxyhornblende. Quartz, 1 percent, occurs in large phenocrysts with resorbed outlines and conchoidal fractures, which tend to aid plucking of this mineral during grinding of the thin section. Anhedral magnetite forms 1 percent of the rock. The groundmass consists of clear pinkish glass (N=1.491) containing numerous small vesicles.

References:
Geology of Little Sitkin Island, Alaska

GEOCHEM DATA
StationIDLatitudeLongitudeGeologistDateVisitedAge InfoVolcanoEruptionLocation 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
Snyder_1959_1351.9531178.5356Snyder, G. L. Little SitkinPratt Point member of Little Sitkin dacite. Collected from within 6 inches of contact with rock represented by analysis, 7 (Little Sitkin dacite from coast half a mile north of Pratt Point)Rhyodacite lava from Pratt Point member of Little Sitkin dacite. Color: yellowish gray (5 P 7/1). Texture: hypocrystalline, vesicular, porphyritic with plagioclase phenocrysts as much as 5 mm and hornblende phenocrysts as much as 3 mm long. Plagioclase megaphenocrysts, 15-20 percent, are complexly zoned from cores of An55-60 to rims of An35-45; several feldspars poikilitic with small hornblende inclusions, 0.09 by 0.2 mm; minute clinopyroxene rods, 0.01 by 0.05 mm; and two-fluid inclusions in cavities with a maximum diameter of 0.04 mm. Hornblende, 36 percent, is pleochroic in shades of olive green, reddish brown, and black; several crystals have deeper pleochroism at borders than at center. Hypersthene, 1-2 percent, is the only pyroxene megaphenocryst; two crystals have a core of oxyhornblende. Quartz, 1 percent, occurs in large phenocrysts with resorbed outlines and conchoidal fractures, which tend to aid plucking of this mineral during grinding of the thin section. Anhedral magnetite forms 1 percent of the rock. The groundmass consists of clear pinkish glass (N=1.491) containing numerous small vesicles.Snyder_1959_13Whole Rock 69.64 0.33 15.22 3.2 0.11 0.94 3.42 4.47 2 0.13 99.83424NN1.341.99H2OM=0; H2OP=0.52; CO2=0NN 43.7 248 6.1 745XRFB V=0.002, M=SPEC, R=424;Ba V=0.05, M=SPEC, R=424;Sr V=0.04, M=SPEC, R=424;K V=1.66, M=NN, R=745;Yb V=0.0002, M=SPEC, R=424;Y V=0.001, M=SPEC, R=424;Zr V=0.008, M=SPEC, R=424;Co V=0.0004, M=SPEC, R=424;Cr V=0.0001, M=SPEC, R=424;Cu V=0.001, M=SPEC, R=424;V V=0.005, M=SPEC, R=424;Ga V=0.001, M=SPEC, R=424;Sc V=0.0002, M=SPEC, R=424;Mo V=0.0003, M=SPEC, R=424;

SAMPLE LOCATION

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