Comparison of Oxygen Isotope Analyses of Tektites, Soils, and Impactite Glasses

Abstract

New oxygen isotope analyses of tektites from various localities were made, including two philippinites from Isabela, Philippine Islands, one of which contains small Ni-Fe spherules (CHAO and others [1961]); a billitonite; a Muong Nong-type tektite, as well as a normal type, from Phang Daeng, Thailand; a Georgia tektite; and seven bediasites. The total range in δ-values for 24 tektites from widely separated occurrences is 8.9 to 10.8 per mil, relative to mean ocean water. Eight isotopic analyses of bediasites exhibit a good correlation with index of refraction, density, and SiO_2 content. The higher the O(^18)/O^(16) ratio the lower is the SiO_2 content. The other analyzed tektites do not show this correlation. Thirteen randomly selected soils of various types (11 from the U.S.A.) have δ-values ranging from 10.0 to 15.9 per mil, and a series of samples from a soil profile in Georgia show a progressive increase of 5 per mil from the fresh granite up to the clay-rich B zone; sandy A zone material is 3 per mil lower in O(^18)/O^(16) than the immediately underlying B zone. Two soil samples were selected for fusion experiments; it was found that melting increased the O(^18)/O^(16) ratios of soils by about 1 per mil. Inasmuch as it would require a 3.5-4.0 per mil lowering of O(^18)/O^(16) in soils to bring them into the tektite range, they appear to be unlikely parent materials for tektites. Four samples of impactite glass (Ries-2 samples, Wabar, and Henbury) give δ -values of 7.9, 9.0, 12.7, and 14.4. Dense, clean glass from the Hies Kessel, the sample which most closely resembles tektite glass in appearance, gave the smallest δ-value. The oxygen isotope data suggest that tektites are either fused terrestrial granitic rocks (with changed chemical composition), or they are extraterrestrial.