PLATINUM-GROUP ELEMENTS AND SILVER IN THE CRETACEOUS-TERTIARY BOUNDARY SAMPLES FROM STEVNS-KLINT, DENMARK

Ru, Pd, Ir, Pt and Ag in two Cretaceous-Tertiary boundary Danish sampl es and in the Orgueil carbonaceous chondrite were determined by isotop e dilution employing the inductively coupled-plasma mass spectrometer. Some mutual abundance fractionation potentially reflecting the differ ence in metal density can be recognized among the platinum-group eleme nts (PGE). Silver is anomalously enriched by a factor of 15 compared w ith PGE, on the basis of ''cosmic'' abundances. This enrichment of Ag can be interpreted as indicating the precipitation of silver sulfide f rom seawater. Sulfate reduction to sulfide anion in seawater is sugges ted as an explanation of anomalous enrichment of Ag and Re.