Genetic relations between iron and stony meteorites

The main group pallasites and the mesosiderites fall within the oxygen isotope group previously determined for the calcium-rich achondrites (eucrites, howardites and diogenites), consistent with derivation from a common source material, and perhaps a common parent body. The group IIE iron meteorites were derived from the same source material as H-group ordinary chondrites. The chondrite-like silicate inclusions in group IAB iron meteorites are not related to the ordinary chondrites, but may be related to the enstatite chondrites. Several meteorites previously considered “anomalous” fall into these groups: Pontlyfni and Winona with the IAB irons, and Netschaëvo possibly with the H chondrites and IIE irons. The unusual pallasites Eagle Station and Itzawisis have remarkable oxygen isotopic compositions, and have more of the ¹⁶O-rich component than any other meteorite. Bencubbin and Weatherford are also unusual in their isotopic compositions, and may bear some relationship to the C2 carbonaceous chondrites. Lodran and Enon are isotopically similar to one another and are close to the achondrite-mesosiderite-pallasite group.