Nanodiamond of Meteorites: Concentrations and Isolation Kinetics of Possible Initial Xenon Components

A. V. Fisenko & L. F. Semjonova

Geochemistry International, Volume 60, pages 530–536
Published: 06 June 2022


“The uncertainty in the isotope compositions of the initial (primary) xenon components responsible for its measured composition in meteoritic nanodiamonds requires a more in-depth analysis of these data and modeling using different initial compositions. In this work, we analyzed for the first time the contents of xenon components in nanodiamond-enriched fractions of Orgueil (C1) and Indarch (EH3-4) meteorites. These contents were calculated assuming that Xe-HL and Xe-P6e consist of a mixture of Xe-P3 and isotopically anomalous subcomponents, designated by us as Xe-pr1 and Xe-pr2, respectively. The last two components could have been formed in the p- and r-processes of nucleosynthesis during explosion of a type II supernova. The isotope compositions of the Xe-pr1 and Xe-pr2 components were calculated assuming that Xe-P3 is an almost isotopically normal component in the Xe-HL and Xe-P6e components. Based on the calculated contents of initial Xe-P3, Xe-pr1, and Xe-pr2 components in nanodiamonds of such meteorites as Indarch (EH3-4) and Orgueil (C1), the following conclusions are made: (1) Each of the Xe-pr1, Xe-pr2, and Xe-P3 components is found in the individual populations of diamond grains with different thermo-oxidative stability. Based on the relative contents of xenon components, Xe-P3 is the major component. (2) According to the Ott model (Ott, 1969), the differences between the Xe-pr1 and Xe-pr2 components in 124Xe/136Xe and 134Xe/136Xe isotopic ratios are probably related to the limited time of formation of Xe isotopes through the decay of their radioactive precursors from the moment of supernova explosion to their capture: 1.89 hours for Xe-pr2 and 2.17 hours for Xe-pr1. It is suggested that carrier phases of Xe-pr1 and Xe-pr2 components are formed in different turbulent mixing zones of fragments of the outer and inner layers of type II supernovae.”