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A large (130 g), layered tektite was found just south of Riddleville, Georgia, USA, in July 1993. The specimen has a bulk composition similar to that of splash-form Georgia tektites, but with a much wider range in composition (e.g., the silica content ranges from 69–99 wt%) and it contains numerous white opaque inclusions. Portions of the specimen were studied to determine the petrography, major and minor element, and strontium and neodymium isotopic composition, water content, magnetic properties, ferric/ferrous ratio, and 40 Ar/ 39 Ar age. The white opaque inclusions were found to be zircon crystals, many of which had partly or completely decomposed to baddeleyite plus SiO 2 glass. The trace element, strontium and neodymium isotopic ratios, water content, age (∼34.5 Ma), and magnetic properties are all similar to normal Georgia tektites. Mo¨ssbauer data indicate Fe 3+ /Fe 2+ ratios between 0.07 and 0.16. This specimen has all the characteristics of a Muong Nong-type tektite, except that it is not as strongly enriched in volatile elements, including water, as are the Australasian Muong Nong-type tektites. The lack of a strong enrichment in volatile elements, plus the fact that many of the included relict zircons have partly or completely broken down to baddeleyite plus SiO 2 glass, indicates that this specimen was heated more intensely than most zircon-bearing Australasian Muong Nong-type tektites. The occurrence in the northeastern corner of the Georgia strewn field is consistent with a proposed source crater near Deep Sea Drilling Project Site 612 off the coast of New Jersey. |
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