title: Uranium and thorium abundances in chondritic meteorites.
abstract: Neutron-activation analyses for uranium and thorium are reported for 42 chondrite meteorite "falls" and 1 "find" covering 15 of the 20 Van Schmus-Wood chondrite types. The mean uranium and thorium abundances of the 5 chemical groups show a trend with C group (U = 0.012(0) atoms/10(6) Si atoms, Th = 0.045(4) atoms/10(6) Si atoms, Th U = 3.7(8)) > H, L and LL groups (U = 0.008(3), Th = 0.028(0), Th U = 3.4(5)) > E group (U = 0.005(9), Th = 0.021(8), Th U = 3.6(9)). With the possible exception of the C3 chondrites, the mean abundances for each petrologic type within a given chemical group are identical.
authors.affiliation: Department of Geophysics and Geochemistry, The Australian National University, Canberra A.C.T. 2600, Australia.
authors.forename: J W
authors.initials: JW
authors.lastname: Morgan
authors.forename: J F
authors.initials: JF
authors.lastname: Lovering