ANOMALOUS NOBLE-GASES IN JOSEPHINITE AND ASSOCIATED ROCKS

In this paper we report Ne, Ar, Kr and Xe analyses of josephinite, Josephine Peridotite, and serpentinized Josephine Peridotite. In all three samples the elemental abundance patterns resemble patterns associated with surface waters, the Ne data do not exhibit the large 21Ne enrichments observed earlier, and the Kr and Xe compositions are indistinguishable from atmospheric composition at all isotopes, including 129Xe. Our data thus offer no significant evidence for isotopic anomalies in the noble gases. We also argue that the previous claims for primordial atmospheric-like Ar, anomalous Kr and Xe, excess 129Xe, and 4.6 × 109-year age are all questionable interpretations which cannot be defended against more prosaic alternatives. This leaves excess 21Ne as the only noble gas argument for exotic origin; we suggest that this might be an experimental artifact. Until the 21Ne question can be settled by more definitive experimentation, we feel that noble gas data cannot be used to support arguments that the origin of josephinite is more exotic than crustal serpentinization. © 1979.