Platinum and gold in chondritic meteorites

Abstract

Platinum and gold have been determined simultaneously in 43 chondrites by neutron activation analysis. A rapid radio-chemical procedure employing a substoichiometric separation of gold was used. Platinum was determined by counting the 0.159 MeV gamma-rays of 199Au (the radioactive daughter of 199Pt) and gold was determined by counting the 0.412 MeV gamma-rays of 198Au. The atomic abundances relative to Si = 10 6 atoms for the C1/C2/C3 carbonaceous chondrites are found to be 1.34/1.07/1.43 for platinum and 0.19/0.20/0.18 for gold, respectively. The L- and LL-group chondrites were found to be uniformly depleted in platinum and gold with respect to the carbonaceous chondrites while the H-group chondrites exhibit abundances similar to the carbonaceous chondrites. The enstatite chondrites are enriched in gold but have platinum abundances similar to those in the carbonaceous chondrites suggesting a fractionation among the noble metals in their formation. Platinum and gold are positively correlated within each major chondrite group and, if all analyses of this work are considered, yield a correlation coefficient of 0.70 which is significant at the 99.9% confidence level.