National Geochronological Database sample #12942

Outcrop or artificial surface exposure, Quartz monzonite

Geographic location
-117.588333, 36.251667
117° 35' 18" W, 36° 15' 6" N
Inyo county, CA
Darwin 1:62,500 scale map quadrangle
Accurate to within 1 minute (~1 mile)
ROAD 3.2 KM SOUTH OF DARWIN
Source of sample Outcrop or artificial surface exposure
Rock name Quartz monzonite
Description QUARTZ MONZONITE OF COSO PLUTON
Laboratories University of California, Santa Barbara
Compiler name Singh, P.
Date compiled 1983 06
Precision of location Accurate to within 1 minute (~1 mile)
Location comment ROAD 3.2 KM SOUTH OF DARWIN
Bibliographic reference Chen, J.H., and Moore, J.G., 1982, Uranium-lead isotopic ages from the Sierra Nevada Batholith, California: Journal of Geophysical Research, v. 87, No. B6, p. 4761-4784.
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Geologic map unit -117.588333, 36.251667
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U-Th-Pb age determinations

Age estimates
155.9Ma by 206Pb/238U
156.1Ma by 207Pb/235U
161Ma by 207Pb/206Pb
Rock or mineral analyzed zircon
-200+325 MESH FRACTION
Analytical details
Lab sample ID 78 COSO-1(M)S
Decay constants 1.55125E-04, 9.8485E-04, 4.9475E-05
204Pb concentration 0.159
206Pb concentration 71.23
207Pb concentration 5.808
208Pb concentration 22.8
Comments on analysis 238U=628 PPM, 206PB=13.27 PPM
Comments PLUTON IS AROUND 156 M.Y. OLD
Age estimates
157.1Ma by 206Pb/238U
158.5Ma by 207Pb/235U
180Ma by 207Pb/206Pb
Rock or mineral analyzed zircon
+200 MESH FRACTION
Analytical details
Lab sample ID 78 COSO-1(C)S
Decay constants 1.55125E-04, 9.8485E-04, 4.9475E-05
204Pb concentration 0.192
206Pb concentration 70.01
207Pb concentration 6.294
208Pb concentration 23.51
Comments on analysis 238U=642 PPM, 206PB=13.70 PPM
Comments PLUTON IS AROUND 156 M.Y. OLD