Initial strontium for a chondrite and the determination of a metamorphism or formation interval
Abstract
A precise Rb-Sr internal isochron was determined for Guarena, an H6 chondrite, yielding an age of 4.56 ± 0.08 × 10⁹ years. Rb-poor, Sr-rich phosphate phases (whitlockite and apatite) were obtained resulting in a precise measurement of the initial Sr isotopic composition (⁸⁷Sr/⁸⁶Sr)_I = 0.69995 ∓ 0.00015. It is shown that from precise age and initial (⁸⁷Sr/⁸⁶Sr)_I measurements we can obtain information on the differential evolution of Rb-Sr systems involving either simple metamorphism of closed systems or multi-stage processes. The high initial ratio obtained for Guarena with respect to the value for the basaltic achondrites is the first clear demonstration of differential Sr evolution of a chondrite and affords the simple explanation of Guarena having been metamorphosed 74 million years after its formation. This approach may yield a "time" evolution index for the classification of meteorites.
Additional Information
© 1969 Published by Elsevier B.V. Received 5 August 1969. We thank Mr. J.Brown for his competent and meticulous work in obtaining the phosphate separates. This research was principally supported by grants from the National Science Foundation (GP-9433 and GP-9114).Additional details
- Eprint ID
- 115201
- DOI
- 10.1016/0012-821x(69)90008-9
- Resolver ID
- CaltechAUTHORS:20220617-310969500
- NSF
- GP-9433
- NSF
- GP-9114
- Created
-
2022-06-17Created from EPrint's datestamp field
- Updated
-
2022-06-17Created from EPrint's last_modified field
- Other Numbering System Name
- Caltech Division of Geological Sciences
- Other Numbering System Identifier
- 1655