National Geochronological Database sample #1201

Outcrop or artificial surface exposure, Andesite

Geographic location
-117.155556, 37.695833
117° 9' 20" W, 37° 41' 45" N
Nye county, NV
Goldfield 1:62,500 scale map quadrangle
Accurate to within 0.1 minute (~500 feet)
SE 1/4 SW 1/4 NE 1/4 SEC. 9, T1S, R43E, CLIFF FACE ON BLACKCAP MOUNTAIN (TOWNSHIP SHOULD BE T3S---COMPILER)
Source of sample Outcrop or artificial surface exposure
Rock name Andesite
Description LOWER FLOW OF LABBRADORITE ANDESITE CAPPING BLACKCAP MOUNTAIN. ANDESITE IS DARK GRAY TO BLACK, MEAGERLY PORPHYRITIC WITH PHENOCRYSTS OF ZONED PLAGIOCLASE (AN50-70), TITANAUGITE, AND IDDINGSITIZED OLIVINE IN A GROUNDMASS OF MICROLITES OF PLAGIOCLASE, PYROX
Laboratories Yale
Compiler name Marvin, R.F.
Date compiled 1976 04
Precision of location Accurate to within 0.1 minute (~500 feet)
Location comment SE 1/4 SW 1/4 NE 1/4 SEC. 9, T1S, R43E, CLIFF FACE ON BLACKCAP MOUNTAIN (TOWNSHIP SHOULD BE T3S---COMPILER)
Bibliographic reference Armstrong, R.L., Dick, H., and Vitaliano, C.J., 1972, K-Ar Dates and Strontium Isotope Initial Ratios Of Some Cenozoic Volcanic Rocks From West-Central Nevada: Isochron/West, no. 3, p. 23-28.
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Geologic map unit -117.155556, 37.695833
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K-Ar age determinations

Age estimate 13.31 ± 1.2Ma
age of volcanism
Type of analysis conventional K-Ar
POTASSIUM VALUE IS CONVERTED AVERAGE OF 1.40% AND 1.39% K; ARGON VALUE IS CONVERTED AVERAGE OF 0.00000067 AND 0.00000078 CC/G; OTHER RADIOGENIC ARGON VALUE IS 6%
Rock or mineral analyzed whole rock
Analytical details
Lab sample ID Y-B2-3
Decay constants 4.72E-04, 0.584E-04, 1.19E-04*
K2O concentration 1.68 %
Radiogenic 40Ar concentration 0.323
Radiogenic Ar 8 %