ORIGIN OF TEKTITES

The origin of tektites has been obscure because of the following dilem ma. The application of physical principles to the data available on te ktites points strongly to origin from one or more lunar volcanoes; but few glasses of tektite composition have hitherto been reported from t he lunar samples. Instead, the lunar silicic glasses consist chiefly o f a material very rich in K2O and poor in MgO. The ratio of K2O/MgO is higher in these glasses than in any tektites reported. The solution o f the dilemma seems to come from the study of some recently discovered terrestrial deposits of tektite glass with high values of K2O/MgO at the Cretaceous-tertiary boundary. These glasses are found to be very v ulnerable to crystallization into sandine or to alteration to smectite . These end products are known and are more abundant than any terrestr ial deposits of tektite glass. It seems possible that, in fact, the mo on produces tektite gf ass, mostly of the high K2O-low MgO type; but o n Earth these deposits are destroyed. The much less abundant deposits with lower K and higher Mg are observed because they survive. Other ob jections to the lunar origin hypothesis appear to be answerable.