A MUONG NONG-TYPE GEORGIA TEKTITE

A large (130 g), layered tektite was found just south of Riddleville, Georgia, USA, in July 1993. The specimen has a bulk composition simila r 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 i t contains numerous white opaque inclusions. Portions of the specimen were studied to determine the petrography, major and minor element, an d strontium and neodymium isotopic composition, water content, magneti c properties, ferric/ferrous ratio, and Ar-40/Ar-39 age. The white opa que inclusions were found to be zircon crystals, many of which had par tly or completely decomposed to baddeleyite plus SiO2 glass. The trace element, strontium and neodymium isotopic ratios, water content, age (similar to 34.5 Ma), and magnetic properties are ail similar to norma l Georgia tektites. Mossbauer data indicate Fe3+/Fe2+ ratios between 0 .07 and 0.16. This specimen has all the characteristics of a Muong Non g-type tektite, except that it is not as strongly enriched in volatile elements, including water, as are the Australasian Muong Nong-type te ktites. The lack of a strong enrichment in volatile elements, plus the fact that many of the included relict zircons have partly or complete ly broken down to baddeleyite plus SiO2 glass, indicates that this spe cimen 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.