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Published May 1971 | public
Journal Article

Lunar chronology and evolution from Rb-Sr studies of Apollo 11 and 12 samples

Abstract

Rb-Sr internal isochrons for a total of eight Apollo 12 crystalline rocks yield ages of 3.36 to 3.16 AE. The initial Sr compositions (I) are relatively primitive and range from 0.69918 to 0.69957 as compared to BABI= 0.69898 ± 3. No clear groupings inI are observed, however, the wide range indicates that at least four different rock bodies were sampled. An Apollo 11 basalt (10024) yielded an age of 3.61 ± 0.07AE and I = 0.69935 ∓ 8 in agreement with previous results on other Apollo 11 high K rocks. Several Apollo 12 soil samples yield model ages which range from 4.4 to 4.6 AE and indicate that the special nature and older "age" of the lunar soil determined at the Apollo 11 site is a widespread phenomenon. Initial Sr compositions from Apollo 11 and Apollo 12 support our previous conclusions that the moon as a whole has a Rb/Sr much lower (Rb/Sr ≈ 0.008) than found in chondrites. We summarize the current status of Rb-Sr lunar chronology and some implications regarding the melting and differentiation history of the moon.

Additional Information

A. Albee and D. Burnett provided continuous support and cogent comments on the manuscript. We benefited from heated discussions with G. Turner. It was a privilege to have the skillful support of Pai Young and Al Massey and of T. Wen, Lily Ray and J. Brown. The high purity HF was still provided by M. Tatsumoto. This work was supported by NASA contract NAS-9-8074 and by NSF grant GP-19887.

Additional details

Created:
August 22, 2023
Modified:
October 24, 2023