THE BURNWELL, KENTUCKY, LOW IRON-OXIDE CHONDRITE FALL - DESCRIPTION, CLASSIFICATION AND ORIGIN

The Burnwell, Kentucky, meteorite fell as a single stone on 1990 Septe mber 4. The Burnwell meteorite has lower Fa in olivine (15.8 mol%), Fs in orthopyroxene (13.4 mol%), Co in kamacite (0.36 wt%), FeO from bul k chemical analysis (9.43 wt%), sind Delta(17)O (0.51 +/- 0.02 parts p er thousand), and higher Fe, Ni, Co metal (19.75 wt% from bulk wet che mical analysis) than observed in H chondrites. The Burnwell meteorite plots on extensions of H-L-LL chondrite trends for each of these prope rties towards more reducing compositions than in H chondrites. Extensi ons of this trend have been previously suggested in the case of other low-FeO chondrites or silicate inclusions in the IIE iron Netschaevo, but interpretation of the evidence in these meteorites is complicated by terrestrial weathering, chemical disequilibrium or reduction. In co ntrast, the Burnwell meteorite is an equilibrated fall that exhibits n o evidence for reduction. As such, it provides the first definitive ev idence for extension of the H-L-LL ordinary chondrite trend beyond typ ical H values towards more reducing compositions.