Rare gases in the chondrite pantar

Abstract

Ne and He studies by König and co-workers for the chondrite Pantar have been confirmed, and the measurements have been extended to include Ar and Xe. The light phase of this meteorite is typical of most chondrites in its content of radiogenic He4 and Ar40 and cosmogenic He3, neon, and argon. The dark phase, in which opaque minerals outline the chondrules, is rich in ‘primordial’ rare gases. Primordial xenon, exhibiting ‘general’ isotopic anomalies identical to those found in carbonaceous chondrites, occurs in both phases but is 12 times more abundant in the dark phase. Radiogenic Xe129 from I129 decay occurs in both phases but is 53 times more abundant in the dark phase. The primordial gas spectrum resembles other meteorites in its He/Ne and Xe/Ar ratios. In its Ar/Ne and Ne20/Ne22 ratios it resembles Pesyanoe and belongs to what can be loosely described as a ‘cosmic’ group of gas-rich stones.