Tibooburra, a New Australian Meteorite Find, and Other Carbonaceous Chondrites of High Petrologic Grade

Petrological evidence suggests that the Tibooburra meteorite from western New South Wales, like the Allende meteorite, is a CV3 chondrite which has experienced greater metamorphic effects than others of its class. The transitional nature of its bulk composition, which is intermediate between the CO and CV chondrites, is exhibited by several elements and displayed by the multivariate techniques of cluster analysis and principal component analysis. Tibooburra therefore resembles such CV chondrites as Coolidge and Karoonda, which have accreted early in the history of the Vigarano parent body and consequently possess a higher content of high-temperature, Ca-Al-rich inclusions with fewer low-temperature matrix and volatile phases than other CV chondrites. Both the matrix and magnesium silicate phases of these meteorites seem more iron-rich than those in later-accreted meteorites.