A comparison between terrestrial impact glasses and lunar volcanic glasses: The case of fluorine

Abstract

The genetic relationship between tektites (and several other terrestrial impact glasses) and lunar volcanic glasses has long been a point of discussion. With the aid of new fluorine data we try to furnish new evidence for the view that tektites are distinct from and bear no chemical relationships to lunar volcanic glasses. Since fluorine analyses are only rarely made for the kind of material in question, we discuss here our procedures of fluorine determinations with reference to methods newly developed in our laboratory. The first method involves ion sensitive electrode techniques, while the second uses rapid instrumental neutron activation analysis (RINAA). The results of our determinations of fluorine in tektites and other terrestrial impact glasses are presented and discussed together with data of lunar glasses acquired from the literature. The difference between the chemical behaviour of tektites and lunar glasses is also found in the fluorine data. It is shown that the expectation of high fluorine contents of tektites as it may be inferred from well documented high fluorine contents of lunar volcanic glasses as well as a possible connection between tektites and these glasses could not be sustained with the aid of chemical data. Thermodynamical data, calculated for conditions of lunar volcanoes, leads to the conclusion that several volatile elements are abundant during lunar lava fountaining and should correlate in volcanic glasses. Tektites fail to show these correlations, as it is pointed out with the aid of correlation analyses. Our data leads consequently to the conclusion that there are severe chemical differences between tektites and lunar volcanic glasses.