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North American localities, Part 2 of Uranium-lead method of age determination

Walter R. Eckelmann and John Laurence Kulp
North American localities, Part 2 of Uranium-lead method of age determination
Bulletin of the Geological Society of America (September 1957) 68 (9): 1117-1140


Many new isotopic age determinations by the uranium-lead method have been made on most of the important North American localities from which primary uranium minerals have been reported. With the aid of other published isotopic U-Pb age measurements the writers attempted to interpret the most probable age for each locality and to assign a reasonable uncertainty to that age. The recognition of differential lead loss, the relation of alteration to mineral type, the importance of radon leakage for young samples, and the potential analytical errors make it timely to conduct: such a re-evaluation. Among the well-established ages are: Spruce Pine district, North Carolina, 360 + or - 20 m.y.; Portland, Connecticut, 265 + or - 10 m.y.; Front Range, Colorado, 59 + or - 5 m.y.; Black Hills, South Dakota, 1620 + or - 20 m.y.; southeast Manitoba, 2650 + or - 100 m.y.; Lake Athabasca, Saskatchewan, 1900 + or - 50 m.y.; and the Wilber-force area, 1050 + or - 20 m.y. Other probable ages are Bedford, New York, 350 m.y.; Colorado Plateau, 60 m.y.; Coeur d'Alene, 1200 m.y.; and Great Bear Lake, Northwest Territories, 1500 m.y. Although there may have been several regional metamorphic events in the Appalachian Province in the Precambrian, the post-Cambrian effects appear at only two periods centering on 260 m.y. and 360 m.y. The Grenville metamorphism appears limited to a narrow time interval about 1050 m.y. ago. The Front Range and Colorado Plateau uranium mineralization may have been one event occurring about 60 m.y. ago.

ISSN: 1050-9747
Serial Title: Bulletin of the Geological Society of America
Serial Volume: 68
Serial Issue: 9
Title: North American localities, Part 2 of Uranium-lead method of age determination
Pages: 1117-1140
Published: 195709
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
Accession Number: 1959-008662
Categories: Mineralogy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from Bibliography and Index of North American Geology, U. S. Geological Survey, Reston, VA, United States
Update Code: 1959
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