National Geochronological Database sample #2816

Outcrop or artificial surface exposure, Granodiorite

Geographic location
-143.826667, 61.74
143° 49' 36" W, 61° 44' 24" N
AK
McCarthy C-8 1:63,360 scale map quadrangle
Accurate to within 1 minute (~1 mile)
WRANGELL MOUNTAINS
Source of sample Outcrop or artificial surface exposure
Rock name Granodiorite
Description FINE-GRAINED BIOTITE-HORNBLENDE GRANODIORITE; CUTS NIKOLAI GREENSTONE AND SKOLAI GROUP
Laboratories USGS Menlo Park
Compiler name Hambly, P.A.
Date compiled 1977 08
Precision of location Accurate to within 1 minute (~1 mile)
Location comment WRANGELL MOUNTAINS
Bibliographic reference Berry, A.L., Dalrymple, G.B., Lanphere, M.A., and Von Essen, J.C., 1976, Summary Of Miscellaneous Potassium-Argon Age Measurements, U.S. Geological Survey, Menlo Park, California, For The Years 1972-74: U.S. Geological Survey Circular 727, p. 1-12
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Geologic map unit -143.826667, 61.74
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K-Ar age determinations

Age estimate 144.9 ± 4Ma
age not evaluated
Type of analysis conventional K-Ar
Rock or mineral analyzed hornblende
Analytical details
Lab sample ID 71 AMK 26A
Decay constants 4.72E-04, 0.585E-04, 1.19E-04*
K2O concentration 0.813 %
Radiogenic 40Ar concentration 1.766
Radiogenic Ar 76 %