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SAMPLE INFO : 87-AWs-4
Sample ID:87-AWs-4
Station ID:87-AWs-4
Latitude:62.0789
Longitude:-144.4917
Datum:NAD83
Date Sampled:1987-00-00
Sample Type 1:Lava
Sample Type 2:Dome
Field Lithology:Andesite
Text Description:
Mount Drum collapsed dome (Pleistocene). Commonly pale-red, but locally medium-gray where unoxidized, porphyritic hornblende andesite that contains phenocrysts of plagioclase (5-15%, as large as 6 mm), hornblende (2-5%, as large as 2 mm), clinopyroxene (1-3%, 1-2 mm), and hypersthene (0-3%, 0.5-4 mm), in pilotaxitic to glassy groundmass. Dome is mostly a pile of andesite rubble that consists of angular to subrounded blocks as much as tens of meters in diameter, but that average less than 1 m, in pinkish-gray, andesitic, sand- to dust-sized matrix. Part of dome apparently was not disrupted (ruled area). Dome may have been destroyed by violent phreatic explosive activity shortly after emplacement and is probable source of Sanford debris flow (Richter and others, 1988), which is exposed as far as 50 km to northwest where it is interbedded with glacial deposits in Copper River basin. * * *Plagioclase from dome yielded K-Ar age of 0.67+/-0.01 Ma.

References:
Geologic map of the Gulkana A-1 Quadrangle, south-central 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
87-AWs-462.0789-144.4917Unknown, Unknown1987-00-00 670000 ± 10000 K-Ar; 2262; plagioclase K-ArDrumMount Drum rocks within Gulkana A-1 quadrangle. Latitude and longitude derived from paper map.Mount Drum collapsed dome (Pleistocene). Commonly pale-red, but locally medium-gray where unoxidized, porphyritic hornblende andesite that contains phenocrysts of plagioclase (5-15%, as large as 6 mm), hornblende (2-5%, as large as 2 mm), clinopyroxene (1-3%, 1-2 mm), and hypersthene (0-3%, 0.5-4 mm), in pilotaxitic to glassy groundmass. Dome is mostly a pile of andesite rubble that consists of angular to subrounded blocks as much as tens of meters in diameter, but that average less than 1 m, in pinkish-gray, andesitic, sand- to dust-sized matrix. Part of dome apparently was not disrupted (ruled area). Dome may have been destroyed by violent phreatic explosive activity shortly after emplacement and is probable source of Sanford debris flow (Richter and others, 1988), which is exposed as far as 50 km to northwest where it is interbedded with glacial deposits in Copper River basin. * * *Plagioclase from dome yielded K-Ar age of 0.67+/-0.01 Ma.87-AWs-4LavaWhole-rock 61.7 0.55 17.2 4.4 0.07 3.5 6.2 3.97 1.47 0.17 99.922262NN1.832.74H2OP=0.61; H2OM=0.14; CO2=0.12RAPIDA

SAMPLE LOCATION

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