National Geochronological Database sample #16547

Outcrop or artificial surface exposure, Schist

Geographic location
-165.315, 64.578333
165° 18' 54" W, 64° 34' 42" N
AK
Teller 1:250,000 scale map quadrangle
Accurate to within 0.1 minute (~500 feet)
Source of sample Outcrop or artificial surface exposure
Rock name Schist
Description with glauc+chloritoid
Laboratories University of British Columbia
Compiler name Moscati, R.
Date compiled 1992 04
Precision of location Accurate to within 0.1 minute (~500 feet)
Bibliographic reference Armstrong, R.L., Harakal, J.E., Forbes, R.B., Evans, B.W., and Thurston, S.P., 1986, Rb-Sr and K-Ar study of metamorphic rocks of the Seward Peninsula and the southern Brooks Range, Alaska: Geological Society of America Memoir 164, p. 185-202.
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Geologic map unit -165.315, 64.578333
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K-Ar age determinations

Age estimate 162 ± 6Ma
age of metamorphic crystallization
Type of analysis conventional K-Ar
Rock or mineral analyzed muscovite
Analytical details
Lab sample ID 80-91-2
Decay constants 4.962E-04, 0.581E-04, 1.1167E-04
K2O concentration 8.35 %
Radiogenic 40Ar concentration 20.329
Radiogenic Ar 94 %
Comments The avg K-Ar date is older than the avg Rb-Sr date, this may suggest the presence of inherited Ar

Rb-Sr age determinations

Age estimate 149 ± 6Ma
age of metamorphic crystallization
Type of analysis 87Sr/86Sr-87Rb/86Sr isochron (mineral-whole rock)
Rock or mineral analyzed whole rock
Analytical details
Lab sample ID 80-91-2
Decay constants 1.42E-05
Rubidium concentration 166 ppm
Strontium concentration 45.3 ppm
Initial 87Sr/86Sr 0.708
Ratio 87Rb/86Sr 10.69
Ratio 87Sr/86Sr 0.7867
Normal? T
Age estimate 149 ± 6Ma
age of metamorphic crystallization
Type of analysis 87Sr/86Sr-87Rb/86Sr isochron (mineral-whole rock)
Rock or mineral analyzed muscovite
Analytical details
Lab sample ID 80-91-2
Decay constants 1.42E-05
Rubidium concentration 411 ppm
Strontium concentration 66.8 ppm
Initial 87Sr/86Sr 0.708
Ratio 87Rb/86Sr 17.73
Ratio 87Sr/86Sr 0.8016
Normal? T