Noble gas record, collisional history, and pairing of CV, CO, CK, and other carbonaceous chondrites

Concentration and isotopic composition of the light noble gases as well as of Kr-84, Xe-129, and Xe-132 have been measured in bulk samples of 60 carbo naceous chondrites; 45 were measured for the first time. Solar noble gases were found in nine specimens (Arch, Acfer 094, Dar al Gani 056, Graves Nuna taks 95229, Grosnaja, Isna, Mt. Prestrud 95404, Yamato (Y) 86009, and Y 867 51). These meteorites are thus regolith breccias. The CV and CO chondrites contain abundant planetary-type noble gases, but not CK chondrites. Charact eristic features of CK chondrites are high Xe-129/Xe-132 ratios. The petrol ogic type of carbonaceous chondrites is correlated with the concentration o f trapped heavy noble gases, similar to observations shown for ordinary cho ndrites. However, this correlation is disturbed for several meteorites due to a contribution of atmospheric noble gases, an effect correlated to terre strial weathering effects. Cosmic-ray exposure ages are calculated from cosmogenic Ne-21. They range f rom about 1 to 63.5 Ma for CO, CV, and CK classes, which is longer than exp osure ages reported for CM and CI chondrites. Only the CO3 chondrite Isna h as an exceptionally low exposure age of 0.15 Ma. No dominant clusters are o bserved in the cosmic-ray exposure age distribution; only for CV and CK cho ndrites do potential peaks seem to develop at similar to 9 and similar to 2 9 Ma. Several pairings among the chondrites from hot deserts are suggested, but 52 of the 60 investigated meteorites are individual falls.