Foreign inclusions in stony meteorites—III. Rare gases and oxygen isotopes in a carbonaceous chondritic xenolith in the Plainview gas-rich chondrite

Abstract

Measurements of oxygen and rare gas isotopes in a carbonaceous xenolithic inclusion in the Plainview H5 chondrite indicate that the xenolith and Plainview host are of two distinct meteorite types, and that no isotopic exchange has taken place between the two materials since their juxtaposition. The oxygen isotope analysis of the xenolith yields δ- 18O value of 6.5 ± 0.1 % relative to SMOW, a value similar to that of carbonaceous chondrites (C2). Rare gas contents of the xenolith are also similar to those of carbonaceous chondrites. The radiation ages of the xenolith ( 2.9 ± 0.4 Myr ) and the host ( 2.8 ± 0.4 Myr ) are identical. Analyses of the rare gases in a sample of the host material adjacent to the xenolith show that Plainview is gas-rich, i.e., it contains large amounts (52,300 ± 10 −8 cm 3 STP/g 4He) of solar-type trapped gases. We speculate that carbonaceous chondritic material may be more prevalent in the asteroid belt than previously suspected.