SHOCK, REHEATING, AND GAS RETENTION AGES OF CHONDRITES

In order to investigate shock and reheating effects in ordinary chondrites, 71 bronzite, 26 hypersthene and 6 amphoterite chondrites were examined by X-ray diffraction and 39 bronzite and 19 hypersthene chondrites were studied metallographically. In addition, the inert gas contents of 11 bronzites and 4 hypersthene chondrites were measured mass spectrometrically. We have found that virtually all chondrites with short gas retention ages (<2 b.y.) are substantially shocked and reheated, whereas those with ages >3 b.y. are not reheated to any appreciable extent, although they may be strongly shocked. We have concluded that the reheating observed in chondrites is generally related to shock and that these shock-induced reheating events took place before chondrites were ejected from their parent objects. © 1969.