Rare gases in the chondrite Renazzo

A detailed analysis of the rare gas content of the chondrite Renazzo is presented. Fractions of different isotopic composition are separated by heating the sample to successively higher temperatures. The abundance and isotopic composition of the gases is similar to that in the carbonaceous chondrite Murray, with a high percentage of so-called primordial gas. For the light rare gases this primordial component appears to be highly fractionated with respect to the supposed cosmic isotopic ratios. Variations in the isotopic composition of xenon from Renazzo indicate that a minimum of three distinct components are required to describe the situation, and an analysis of this three-component system is presented in terms of ‘correlation planes.’ In terms of this analysis, three possible origins for the isotopic variations are considered. An I127-Xe129 formation interval for Renazzo is measured using an irradiated specimen of the meteorite. A minimum value of 66±6 m.y. is indicated.