Cosmogenic rare gases and the ⁴⁰K-⁴⁰Ar age of the kodaikanal iron meteorite

Abstract

Measurements have been made of the cosmogenic He, Ne, and Ar in the metal phase and of the K-Ar ages of two glass inclusions in the Kodaikanal iron meteorite. The small amounts of cosmogenic rare gas are best interpreted as due to a low cosmic ray exposure age. From empirical production rates, ages of 12, 15 and 15 m.y. were obtained from the ³He, ²¹Ne and ³⁸Ar concentrations, respectively. The ³He/²¹Ne, ³He/⁴He and ⁴He/³⁸Ar ratios are all consistent with low shielding during the exposure. The feldspar and glass have approximately equal K-Ar ages of 3.5 ± 0.1 and 3.3 ± 0.1 × 10⁹ yr, respectively. These results place constraints on possible origins for the glass and feldspar.

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