^(87)Rb-^(87)Sr isochron and ^(40)K-^(40)Ar ages of the norton county achondrite
Abstract
Analysis of seven different portions of Norton County yielded Rb/Sr ratios ranging from 0.15 to 2.3 and permitted the determination of an isochron with high precision. The Rb and Sr concentrations were found to be as low as ∼0.16 ppm. All of the data lie to within their experimental errors on a line in the Sr evolution diagram of slope 0.0654 ± 0.0014, and intercept 0.700 ± 0.002. This determines an age of 4.7 ± 0.1 × 10^9 yr for λ = 1.39 × 10^(−11) yr^(−1). ^(40)K^(40)Ar ages on samples containing 42, 53 and 107 ppm K gave ages of 4.2 – 4.5 × 10^9 yr which are compatible with the Rb-Sr age. The K appears to be concentrated in alkali feldspar grains of about 5–50 microns. The ^(87)Rb^(87)Sr age and primary ^(87)Sr/^(86)Sr value is of sufficient precision to permit the age resolution of meteoritic objects which were formed 0.3 × 10^9 yr apart. No evidence of element redistribution was found for Norton Country as indicated by the consistency of our Rb-Sr and K-Ar results.
Additional Information
© 1967 Elsevier B.V. Received 14 November 1967. This paper is dedicated to Professor H. H. Nininger for his pioneer efforts in finding and collecting meteorites and making them available for scientific research. The samples used in this research were obtained from the Nininger Meteorite Collection at the Arizona State University through the aid of C. W. Moore. An additional sample of the Norton County Meteorite to was provided by W. Nichiporok. We gratefully acknowledge the assistance of T. Wen in the chemical an J mass spectrometric analyses. The electron microprobe data were obtained with the help of A. E. Bence and A. Chodos. This research was supported by grants from the National Science Foundation, NSF GA-464 and NSF GP-5391 and the U.S. Atomic Energy Commission AEC (AT-04-3(427)).Additional details
- Eprint ID
- 37016
- DOI
- 10.1016/0012-821X(67)90033-7
- Resolver ID
- CaltechAUTHORS:20130220-104628650
- NSF GA-464
- NSF
- NSF GP-5391
- NSF
- AT-04-3(427)
- Atomic Energy Commission (AEC)
- Created
-
2013-02-20Created from EPrint's datestamp field
- Updated
-
2021-11-09Created from EPrint's last_modified field
- Caltech groups
- Division of Geological and Planetary Sciences
- Other Numbering System Name
- Caltech Division of Geological Sciences
- Other Numbering System Identifier
- 1497