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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 IDSample Type 1Sample Type 2Final UnitMaterialSiO2TiO2Al2O3FeOTMnOMgOCaONa2OK2OP2O5Total-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_13LavaWhole-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 units are percent 1.66745XRF: Rb, Sr, Ni; NN: K;
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_13LavaWhole-rock H2OM=0; H2OP=0.52; CO2=0NN units are percent 0.05units are percent 0.04 units are percent 0.0002 units are percent 0.001units are percent 0.008 units are percent 0.0002 0.005units are percent 0.0001 0.0004 units are percent 0.001 units are percent 0.001units are percent 0.0003 424SPEC

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