CARBONACEOUS INCLUSION FROM THE KRYMKA LL-CHONDRITE - NOBLE-GASES AND TRACE-ELEMENTS

A black inclusion from the Krymka LL3 chondrite was analyzed for 20 trace elements and five noble gases, by radiochemical neutron activation and mass spectrometry. The trace element pattern somewhat resembles that of C1 or C2 chondrites, but with several unique features. Elements of nebular condensation T ≳ 1000 K (U, Re, Os, Ir, Ni, Pd, Au, Sb and Ge) are essentially undepleted, as in C1 chondrites, but Re Ir is 1.49 × higher than the characteristic Cl value. Among elements condensing below 1000 K, Cs, Se, Te, and In are depleted to approximately C2 levels (~0.6 × C1), whereas Ag, Bi, Tl are enriched to ~ 1.6 × C1. Such enrichments are thought to be characteristic of late nebular condensates. The noble-gas pattern also is unique. Gas contents are higher than in C1s, by factors of 2.6 to 19 for Ne through Xe. The Ar36 Xe132 ratio of 500 is higher than mean values for C1s or C2s (109 or 89) and exceeds even the highest value seen in C3Os, 420, whereas the He4 Ne20 ratio of 62 is much lower than the values for C1s and C2s (200-370). The Xe129 Xe132 and Xe136 Xel32 ratios of 1.040 and 0.320 resemble those of C1 chondrites, and seem to imply typical proportions of radiogenic Xe129 and 'fissiogenic' xenon. It appears that the inclusion represents a new primitive meteorite type, similar to C-chondrites, but probably a late condensate from a region of higher nebular pressure. © 1979.