Notizen: Radiation Ages of Chondrites

Abstract

[1960] (im Erscheinen). The concentrations of tritium and of all the isotopes of helium, neon, and argon have been determined in some chondrites. The technical procedures have been described briefly in previous publications 1 ' 2 . The results pertinent to this note are summarized in a tritium measurement. Our rare gas results agree reasonably well with those of GOEBEL et al. Radiation Ages of ChondritesRadiation ages are calculated from He 3 /H 3 ratios, assuming equal direct production rates for tritium and helium-3. He 4 and A/K ages are estimated on the basis of the average contents of the elements uranium, thorium, and potassium in chondrites which are U = 1.1 • 10 -8 g/g 3 , Th/U = 3.6 4 , and K = 0.085% 5 < 6 . These ages are given in table 2, together with those from chondrites for which He 3 /H 3 radiation ages have been published before 8 . The results from Abee by BEGEMANN et al. 9 are not included here, as this stone is an achondrite according to UREY and MAYEDA 10 . In the histogram (Fig. 1) we have distinguished between two groups of chondrites: those with high and those with low radioactive He 4 and A/K ages. It is remarkable that all the chondrites belonging to the first 6

Untersuchungen an Steinmeteoriten mit extrem hohem Edelgasgehalt

“…Es war möglich, die hellen Anteile praktisch rein zu gewinnen, während die dunklen naturgemäß nicht nur aus den Adern, sondern auch aus dem zwischen den Adern liegenden helleren Material bestanden. 21 Ne ergibt sich daher P3/P21 > 4/1,4 = 2.8 , während an den bisher untersuchten Chondriten Werte zwischen 2,9 und 4,1 gefunden wurden 22 .…”

Collisional records in LL‐chondrites

“…Although relatively few radionuclide concentrations are currently available, these measurements in most cases indicate that heavily shielded cases are rare. Several collisional break-up events were suggested to account for the distribution and clustering of exposure ages (Geiss et al, 1960;Anders, 1964;Marti and Graf, 1992). Variations in T, systematics of different petrographic types among the ordinary chondrites have been identified.…”

Nuclear Effects of Cosmic Rays in Meteorites

“…The early finding (22) of activity in about the expected amount has not been verified. Surprisingly, iron meteorites show little or no hydrogen 3 (43) while a positive result has been reported for the iron phase of a chondrite (44). The observed ratio of helium 3 to helium 4 is difficult to reconcile with the loss of tritium in space.…”