Netschaevo: a new class of chondritic meteorite.

The ratios of refractory elements to silicon and of zinc to silicon indicate that the silicate portion of the Netschaëvo meteorite is an ordinary chondrite. The scarcity of chondrules, the large dimensions (about 100 micrometers) of plagioclase grains, and the low indium content (0.09 nanogram per gram) indicate that Netschaëvo belongs to petrologic type 6. On a diagram of reduced iron versus oxidized iron, Netschaëvo lies along an extrapolation of the LL-L-H ordinary chondrite fractionation trend. The abundances of siderophile elements (nickel, germanium, iridium, and gold) are about 1.6 to 2.0 times greater than in H-group chondrites, and siderophile/nickel ratios are, with one exception, those expected from LL-L-H trends. This evidence indicates that Netschaëvo is an extremely iron-rich member of the ordinary chondrite sequence, and that plausible models to account for the ordinary chondrite sequence must produce materials having iron/silicon ratios 25 percent greater than those in CI carbonaceous chondrites. The existence of Netschaëvo emphasizes that the chondritic meteorites in terrestrial collections are a biased and incomplete selection of primitive solar system materials.