AL-26, NA-22 AND CO-60 IN 2 DRILL CORES AND SOME OTHER SAMPLES OF THEJILIN CHONDRITE

Two drill cores have been taken from the main mass of the Jilin chondr ite, Jilin I. One was bored perpendicular to the 2 pi surface of the f irst exposure stage, the other parallel to this surface, and both inte rsected at the presumed 4 pi center of Jilin's second exposure stage. The probed depths were 65 cm and 105 cm, respectively, with a diameter of 26.5 mm. Fifteen drill core samples, 2 documented samples and 14 s trewn field samples have been analysed for Al-26, Co-60 and Na-22. The reconstruction of the preatmospheric Jilin via Co-60 resulted in slig ht deviations for the center position and for the radius (now R = 80(- 5)(+10) cm) compared to an earlier study in 1985. The Co-60 production rate profile is now almost completely reproduced. A constant producti on rate of Na-22 and of Al-26 during the 4 pi irradiation is confirmed also for the center region. The good linear correlation of Al-26 and Ne-21 yields slightly revised irradiation ages for both stages of t(1) = 7 +/- 1 Ma and t(2) = 0.32(-0.03)(+0.06) Ma.