Netschaëvo: A New Class of Chondritic Meteorite

Abstract

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.

Chronology and petrology of silicates from IIE iron meteorites: evidence of a complex parent body evolution

“…1a), which include recrystallized chondrules typical of those found in type 6 ordinary chondrites (Bunch et al, 1970;Olsen and Jarosewich, 1971;Bild and Wasson, 1977). The silicate mineralogy of these clasts is essentially identical to chondrites (Table 1), containing olivine (Fa 14.1 ), orthopyroxene (Fs 13.6 ), plagioclase and phosphates, although the clasts are richer in orthopyroxene and phosphates, poorer in olivine, and contain mafic silicates more reduced than found in H chondrites.…”

“…As discussed earlier, Netschaëvo and Techado silicates are less differentiated and have compositions similar to those of H chondrites (Bunch et al, 1970;Olsen and Jarosewich, 1971;Bild and Wasson, 1977;Casanova et al,1995). Eugster (1988) determined the absolute 21 Ne and 38 Ar production rates for H chondrites by using the relative chemical element factors reported by Schultz and Freundel (1985) and Freundel et al (1986) and then normalizing these rates to 81 Kr-Kr exposure ages for several chondrites.…”

Chondrule size and related physical properties: A compilation and evaluation of current data across all meteorite groups

“…The apparently unique carbonaceous chondrite LEW 85332 has a mean apparent chondrule diameter of 170 m (Rubin and Kallemeyn, 1990). Chondrules in the chondritic clasts in the Netschaëvo iron meteorite (Bild and Wasson, 1977) range in apparent diameter from 300 to 1200 m with a mean and standard deviation of 720 +360/−240. (Rubin, 1990).…”

Petrology and geochemistry of chondrules and metal in NWA 5492 and GRO 95551: A new type of metal-rich chondrite

“…A reduced, metal-rich ordinary chondrite group (HH chondrites) was proposed for Netschaëvo and linked to the parental material of IIE irons (Bild and Wasson, 1977;Wasson and Wang, 1986;Wasson and Scott, 2011). NWA 5492 is a unique chondrite, linked to GRO 95551 , which is both more metal-rich and more reduced than H chondrites but with a similar siderophile element pattern.…”