National Geochronological Database sample #16527

Outcrop or artificial surface exposure, Quartz diorite

Geographic location
-158.5, 56.233333
158° 30' " W, 56° 14' " N
AK
Chignik A-2 1:63,360 scale map quadrangle
Accurate to within 0.1 minute (~500 feet)
along S fork of the river which flows into Mallard Duck Bay
Source of sample Outcrop or artificial surface exposure
Rock name Quartz diorite
Description altered
Laboratories USGS Menlo Park
Compiler name Moscati, R.
Date compiled 1992 04
Precision of location Accurate to within 0.1 minute (~500 feet)
Location comment along S fork of the river which flows into Mallard Duck Bay
Bibliographic reference Wilson, F.H., 1978, Map showing preliminary results of K-Ar studies in the Chignik and Sutwik Island quadrangles, Alaska: U.S. Geologica Survey Open File Report 78-1064.
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Geologic map unit -158.5, 56.233333
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K-Ar age determinations

Age estimate 21.29 ± 0Ma
age of intrusion
Type of analysis conventional K-Ar
Rock or mineral analyzed biotite
Analytical details
Lab sample ID 77AWs 137
Decay constants 4.962E-04, 0.581E-04, 1.1167E-04
K2O concentration 5.56 %
Radiogenic 40Ar concentration 1.713
Radiogenic Ar 31 %