Oxygen isotope studies on the origin of tektites

O's/O •6 ratios of thirteen tektites from Czechoslovakia, Libya, Texas, Indochina, Philippine Islands, Australia, Java, and Peru have been determined by the fluorine-extraction technique. All but one of these lie in relatively restricted range of Oas/O •6 ratio, with $ -9.6 to 10.4 per mil relative to the ocean-water standard. Tektites are therefore 0.5 to 1.5 per mil heavier than average granitic igneous rocks or about the same as average igneous quartz. The s•mple from Macusan, Peru ($ -12.0), is anomalous and is probably not a true tektite. Six analyzed shales are isotopically heavier than tektites and show a much wider range in values ($ -14.2, 14.8, 15.3, 15.5, 17.6, 18.2). Several detrital sedimentary rocks previously analyzed by Silverman and the present authors have $ values of 10.2 to 15.5; analyzed metasedimentary rocks have $ values of 12.1 to 15.7 per mil. Therefore, tektites are not sedimentary or metasedimentary material fused by lightning or by impact of an astronomical body with the earth. Chemically, tektites are unlike terrestrial igneous rocks, and their oxygen isotopic composition is unlike that of sedimentary or metasedimentary rocks. They therefore may be extraterrestrial objects. Introduction. The origin of tektites has been a subject of controversy for a number of years [Spencer, 1933; Barnes, 1940; Urey, 1957; O'Keefe, 1959; and others]. Some workers have suggested that they represent terrestrial silicate material fused by the impact of meteorites or comets upon the earth. The chemical composition of tektites is very similar to that of many ordinary argillaceous sedimentary rocks and their metamorphosed equivalents. These rocks, which include mudstone, siltstone, shale, slate, phyllite, pelitic schist, etc., are very common at the earth's surface; the probability of fusing such material by the chance impact of an extraterrestrial body with the earth is relatively