National Geochronological Database sample #4258

Outcrop or artificial surface exposure, Granodiorite

Geographic location
-118.45, 38.866667
118° 27' " W, 38° 52' " N
Mineral county, NV
Walker Lake 1:250,000 scale map quadrangle
Accurate to within 1 minute (~1 mile)
AT ELEVATION 5453 FT (1661 M) ON COPPER MOUNTAIN, 6.5 KM SW OF DEADHORSE WELL
Source of sample Outcrop or artificial surface exposure
Rock name Granodiorite
Description GRANODIORITE OF COPPER MOUNTAIN
Laboratories USGS Denver
Compiler name Nichols, S.L.
Date compiled 1978 08
Precision of location Accurate to within 1 minute (~1 mile)
Location comment AT ELEVATION 5453 FT (1661 M) ON COPPER MOUNTAIN, 6.5 KM SW OF DEADHORSE WELL
Bibliographic reference Marvin, R.F. and Cole, J.C., 1978, Radiometric Ages: Compilation A, U.S. Geological Survey: Isochron/West, No. 22, P.3-14.
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Geologic map unit -118.45, 38.866667
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K-Ar age determinations

Age estimate 161 ± 4Ma
age of intrusion
Type of analysis conventional K-Ar
7.36%, 7.43% K20
Rock or mineral analyzed biotite
Analytical details
Lab sample ID USGS(D)-MC-74-BE-882
Decay constants 4.962E-04, 0.581E-04, 1.1167E-04
K2O concentration 7.395 %
Radiogenic 40Ar concentration 17.93
Radiogenic Ar 93 %
Age estimate 158 ± 7Ma
age of intrusion
Type of analysis conventional K-Ar
0.49%, 0.51% K20
Rock or mineral analyzed hornblende
Analytical details
Lab sample ID USGS(D)-MC-74-BE-882
Decay constants 4.962E-04, 0.581E-04, 1.1167E-04
K2O concentration 0.5 %
Radiogenic 40Ar concentration 1.189
Radiogenic Ar 86 %