Concordant 3,676 Myr U–Pb formation age for the Kodaikanal iron meteorite

Abstract

The Kodaikanal iron meteorite contains evidence of intensive chemical activity which, according to Rb–Sr studies1, occurred ∼800 Myr after the formation of the Solar System. Here we report the results of U–Pb isotope analyses on a silicate inclusion from Kodaikanal. Leaching experiments on the two major phases, clinopyroxene (CPX) and alkali-rich glass, indicate a contamination by terrestrial Pb attributable to previous curatorial cutting of this iron meteorite. The leached minerals define concordant U–Pb ages that validate the precise Pb–Pb age of 3,676±3 Myr. These data are consistant with Rb–Sr age determinations1. The absence of initial Pb indicates a fast cooling of the silicate material. This has already been established for the metal phase, and a collisional origin for Kodaikanal is favoured.