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Published December 15, 1969 | Published
Journal Article Open

Correlations between O^(18)/O^(16) ratios and chemical compositions of tektites


The limits of oxygen isotope variation in tektites have been determined by analyzing 33 tektites that cover the widest possible spectrum of chemical compositions. δO^(18) values were obtained for 7 australites (8.9 to 11.0), 4 javaites (9.4 to 10.0), 3 indochinites (9.3 to 10.6), 5 philippinites (9.8 to 10.6), 8 moldavites (10.7 to 11.8), and 6 Ivory Coast tektites (13.0 to 13.6), as well as 2 samples of Darwin glass (14.4 to 14.9). Various tektite groupings based on chemical composition and geographic occurrence all show a systematic increase in O^(18) with decreasing SiO_2 content, similar to that previously found for the bediasites. These systematic correlations must arise either by (1) vapor fractionation of tektite material during impact melting or (2) mixing of a SiO_2-rich igneous component and a low-SiO_2 component formed at a much lower temperature; perhaps the mixing occurred during weathering at the earth's surface or during hydrothermal alteration of silicic igneous rocks either on the earth or the moon.

Additional Information

Copyright 1969 by the American Geophysical Union. (Received June 27, 1969.) We are very grateful to Dean R. Chapman and William H. Pinson, Jr., for contributing the samples analyzed in this study. In particular, Dean Chapman suggested that we do further isotopic work on tektites, and he provided carefully selected samples chosen specifically to cover the entire spectrum of chemical compositions and types that he has delineated among the thousands of Australasian tetkites examined by him. We also wish to thank Eugene M. Shoemaker and' Susan Kieffer for supplying the Meteor Crater samples, and we are grateful for stimulating discussions with E. C. T. Chao and L. S. Walter. This work was supported by NASA grant NGR 05-002-085 and Atomic Energy Commission contract AT (04-3)-427, CALT-427-41. Publications of the Division of Geological Sciences, California Institute of Technology, Contribution 1641.

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