Potentially Primary Xenon Components in Nanodiamond-Enriched Meteorite Fractions: New Isotopic Compositions and Carrier Phases

Abstract

The potential primary component composition of xenon in nanodiamond-enriched fractions (NDFs) of meteorites was determined under the assumption that it contains two almost normal, but different isotopic components (Xe-P3 and Xe-P3n). The Xe-P3n component is contained in the individual population of diamond grains, while the Xe-P3 component is contained in diamond-like rims on the diamond grains. The presence of the Xe-P3n component made it possible to use radioactive products of the classical r-process of nucleosynthesis during a type II supernova explosion to form, according to the hypothesis of Ott (1996), two xenon components with an anomalous isotopic composition (Xe-pr1n and Xe-pr2n) without an increased isotope content of ¹³²Xe relative to the isotope content of ¹³⁶Xe. It is assumed that the implantation (sorption) of isotopes of the Xe-pr1n and Xe-pr2n components into their carrier phases probably occurred in turbulent mixing zones of different compositions in the outer and inner shells of a type II supernova after its explosion. The Xe-pr1n component is contained in an individual population of nanodiamond grains, while the Xe-pr2n carrier phase is first suggested to be SiC-X grains, the evolution of which is associated with a type II supernova. Therefore, when SiC-X grains are destroyed, for example, under laboratory conditions, a mixture of Xe-S and Xe-pr2n components is released, which we denote as Xe-X. Thus, according to the concept we proposed, the primary component composition of xenon consists, in addition to Xe-S, of Xe-P3, Xe-P3n, Xe-pr1n and Xe-X, contained in different individual carrier phases. Successful calculations of the abundances of these components in the NDF of such different meteorites as Murchison CM2 and Allende CV3 and their analysis have shown that the above components may be real components.