The Shaw chondrite,I. The case of the missing metal

The mineralogy, elemental and isotopic composition of the Shaw meteorite indicate that it is a highly metamorphosed L-group chondrite which has lost a portion of its metal and sulfide. The metal which remains has an unusual composition relative to that in other L-group chondrites. It is enriched in Ga, Ge, Ir, Mo, Os, Pt, Re and Ru and depleted in As, Au, Cu and Sb. A comparison of the relative enrichments and depletions in Shaw to those observed in San Cristobal, the extreme end-member of group IAB iron meteorites, shows that the metal phases in these two meteorites have complementary compositions. This implies that the metal in Shaw represents the residual solid of a partial melting process while the missing metal, which drained away, may have gone to form an iron meteorite, like San Cristobal.