Bismuth contents of chondrites

Abstract

A neutron activation technique has been developed for determination of the bismuth concentrations in C-, H-, L- and LL-group chondrites. The technique was tested by duplicate analyses of eight standard rocks and a single synthetic sample. The results obtained for standards AGV-1, BCR-1, DTS-1, G-2, GSP-1 and PCC-1 are the first reported. Our analyses of 14 carbonaceous and 5 equilibrated ordinary chondrite samples have confirmed that Bi is indeed a “strongly-depleted” element in meteorites. The mean Bi abundances in carbonaceous chondrites are 143, 71 and 37 atoms/10 9Si atoms for groups C1, C2 and C3, respectively, which relative to C1 yield ratios of : C1: C2: C3 =1.00: 0.50: 0.26—nearly the same as those predicted by a two-component model. In 12 unequilibrated ordinary chondrites (UOC), the Bi contents generally decrease exponentially with increasing equilibration of the silicate phases although there are apparent exceptions to this trend for chondrites having highly unequilibrated silicates. The Bi concentrations in the UOC correlate well with those of carbon and primordial Ar, Kr and Xe determined by others in these same meteorites.