Geochemistry of impact glasses from the K/T boundary in Haiti - Relation to smectites and a new type of glass

Detailed element analyses were carried out on 12 black and seven yellow glasses from the K/T boundary section at Beloc (Haiti), and of three samples from smectite mantles around black glasses. The results obtained for bulk black and yellow glasses show differences between these, confirming the results of Sigurdsson et al. (1991) and Izett (1991), and the results obtained on individual spherules and shards are in agreement with bulk data. The present data also demonstrate, for the first time, the existence of yellow glass samples with high CaO but low S contents, which might have formed by fusion of various proportions of carbonates and evaporites or carbonates alone. One of the black glasses was found to have higher than average SiO2 and K2O abundances but lower concentrations of all other major elements. This suggests the existence of a third glass type, named the high Si-K variety (HSi,K) glass.