Unequilibrated ordinary chondrites - A tentative subclassification based on volatile-element content

In view of the lack of correlation sometimes encountered between the volatile content and metamorphism measures of primitiveness for unequilibrated ordinary chondrites (UOCs), a tentative classification scheme is developed which is based on volatile content and complements the Sears et al. (1980) scheme based on metamorphism. The classification is based primarily on C and Xe, which are not significantly affected by shock-induced reheating. It is noted that novel clues to the formation of chondrites may be derivable from Xe and C; their concentrations in UOCs vary by a factor greater than 5, yet the Xe/C ratio remains nearly constant at 0.0034 of the solar system ratio.