Computer Science
Scientific paper
Apr 1963
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1963gecoa..27..345b&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 27, Issue 4, pp.345-360
Computer Science
2
Scientific paper
Determinations of ruthenium and osmium in ten chondrites by neutron activation analysis give average concentrations of 0.89 × 10 -6 g Ru / g meteorite and 0.91 × 10 -6 g Os / g meteorite. With proper assumptions these values lead in turn to cosmic abundances (per 10 6 Si atoms) of 1.3 for Ru and 0.73 for Os. The averages cited include Ru and Os concentrations for a carbonaceous chondrite, which, though below average, fall within the range of concentrations found for the non-carbonaceous chondrites. The range in both the Ru and Os concentrations from about 0.6 × 10 -6 g/g to 1.4 × 10 -6 g/g reflects not only the variable amount of metal content in the chondrites, but also the variation in Ru and Os concentrations in the metal phase. Analyses of the separated metal and siliceous phases of two chondrites show a marked enrichment of Ru and Os in the metal phase, and they further show that significant amounts of these elements are present in the siliceous phase. Ruthenium and osmium concentrations in Canyon Diablo troilite are found to be suppressed approximately two orders of magnitude below the chondritic averages, which makes it difficult to attribute the presence of Ru and Os in the siliceous phase of chondrites to sulfide inclusion. The isotopic ratio Os 184 / Os 190 for osmium in meteorites agrees with that in terrestrial material to about 1 per cent, within the limits of experimental error. The experimental uncertainty in determining the ratio Ru 96 / Ru 102 is greater, and as a consequence the agreement of Ru 96 / Ru 102 for ruthenium in meteoritic and terrestrial sources cannot be established to much better than 2-3 per cent. With these limits of experimental accuracy, no conclusive evidence for anomalous isotopic composition of ruthenium or osmium has been found in the samples analysed in this work. For samples in which the uranium concentration approaches that of ruthenium, the corrections necessary to account for fission-produced ruthenium permit incidentally the measurement of the uranium present. Uranium concentrations determined in this manner are reported for a few samples $ncluding the standard rocks G -1 and W -1. Two achondrites, a tektite and several terrestrial samples are found to have ruthenium and osmium concentrations 2-3 orders of magnitude below those in chondrites, giving evidence of the marked depletion of these elements in differentiated silicate matter.
Bate George L.
Huizenga J. R.
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