Computer Science
Scientific paper
Jul 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992metic..27r.245k&link_type=abstract
Meteoritics, vol. 27, no. 3, volume 27, page 245
Computer Science
Scientific paper
Among the achondrites, the ureilites are a most fascinating group, well known for their carbon and diamonds and the structures manifesting shock features. We analyzed 12 specimens for the refractory trace elements Y, Zr, Ba, Hf, Ta, and W by RNAA. The results are presented in Table 1. Some minor and trace elements were determined in addition by INAA and will be presented at the conference. Table 1. Refractory trace elements by RNAA (1 sigma errors: +- 10% Sample Y Zr Ba Hf Ta W ppm ppm ppm ppb ppb ppb Novo Urei 0.34 4.25 0.09 2.82 0.43 110 Kenna 0.88 0.57 120 6.4 140 3200 Goalpara 0.34 0.60 4.6 130 6.0 440 Dingo Pub D. 0.80 1.6 93 140 3.3 120 Nilpena 0.74 1.1 170 62 15 46 Haveroe 0.46 0.04 0.09 2.2 0.32 580 ALH 77257 0.39 0.03 0.25 1.6 1.1 62 ALH 78019 0.67 0.04 0.17 1.2 1.3 80 ALH 78262 0.50 0.03 0.04 0.03 0.8 54 ALH 82106 2.20 0.04 0.02 9.1 1.6 9 PCA 82506 0.41 0.03 0.06 0.7 4.3 200 Y 790981 0.54 0.35 0.65 50 1.6 40 Table 2. Ratios Zr/Hf conc. Sample Zr/Hf Novo Urei 1507 Kenna 89 Goalpara 4.6 Dingo Pub D 11.4 Nilpena 17.6 HAveroe 18.9 ALH 77257 19.2 ALH 78019 32 ALH 78262 857 ALH 82106 4.3 PCA 82506 48 Y 7980981 6.9 The variability of the ratio Zr/Hf, normally a quite constant geochemical value, is very striking (C1 value = 31.6). A pronounced difference in concentrations of trace elements between Antarctic and non-Antarctic ureilites is observed. Only a high degree of differentiation can lead to the observed distribution pattern. Among the achondrites, the ureilites are the lowest in concentrations of refractory elements, but are quite rich in Co and Cr, compared to these elements in eucrites. A similar composition is found in some terrestrial dunites. This finding may shed some light on the possibilities of formation of this fascinating class of achondrites. We acknowledge the financial support of the Swiss National Science Foundation and the generous supply of meteoritic samples by NASA.
Burger Marc
Krähenbühl Urs
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