National Geochronological Database sample #397

Outcrop or artificial surface exposure, Granodiorite

Geographic location
-153.615556, 61.381111
153° 36' 56" W, 61° 22' 52" N
Lime Hills B-2 1:63,360 scale map quadrangle
Accurate to within 1 second (~100 feet)
Source of sample Outcrop or artificial surface exposure
Rock name Granodiorite
Laboratories USGS Menlo Park
Compiler name Madden, C.T.
Date compiled 1974 11
Precision of location Accurate to within 1 second (~100 feet)
Location comment ALASKA PENINSULA
Bibliographic reference Reed, B.L., and Lanphere, M.A., 1969, Alaska-Aleutian Range Batholith: Geological Society of America Bulletin, v. 80, p. 2583-2610.
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Geologic map unit -153.615556, 61.381111
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K-Ar age determinations

Age estimate 41.44 ± 1.1Ma
initial age disturbed by later metamorphism
Type of analysis conventional K-Ar
Rock or mineral analyzed biotite
Analytical details
Lab sample ID 82
Decay constants 4.72E-04, 0.585E-04, 1.19E-04*
K2O concentration 8.98 %
Radiogenic 40Ar concentration 5.42
Radiogenic Ar 80 %
Additional reference Reed and Lanphere (1972); Reed and Lanphere (1969)