Sample records for australites

  1. Beryllium-10 in Australasian tektites - Evidence for a sedimentary precursor (United States)

    Pal, D. K.; Moniot, R. K.; Kruse, T. H.; Herzog, G. F.; Tuniz, C.


    Each of seven Australasian tektites contains about 100 micron atoms of beryllium-10 (half-life, 1.53 million years) per gram. Cosmic-ray bombardment of the australites cannot have produced the measured amounts of beryllium-10 either at the earth's surface or in space. The beryllium-10 contents of these australites are consistent with a sedimentary precursor that adsorbed from precipitation beryllium-10 produced in the atmosphere. The sediments must have spent several thousand years at the earth's surface within a few million years of the tektite-producing event.

  2. Tektite Suborbital Science (United States)

    Harris, T. H. S.


    The australite fall sites in S. Australia at 10 km/s require loft times of 7.5 hrs from Indochina and 112.5 deg Earth spin, inconsistent with a launch from that same hemisphere. Alternative AA source regions must explain these imprint elements.

  3. Tektite Process Constraints (United States)

    Harris, T. H. S.


    Shock accounts for only half of "australite" tektites 10 km/s morphologically derived speed. 5,000 m/s delta V remains unaccounted. In perspective, this is equivalent to ~50 years of geosynchronous station keeping budget, and 3/4 of the tektite's KE.

  4. Coeval ages of Australasian, Central American and Western Canadian tektites reveal multiple impacts 790 ka ago (United States)

    Schwarz, Winfried H.; Trieloff, Mario; Bollinger, Klemens; Gantert, Niklas; Fernandes, Vera A.; Meyer, Hans-Peter; Povenmire, Hal; Jessberger, Elmar K.; Guglielmino, Massimo; Koeberl, Christian


    High resolution 40Ar-39Ar step heating dating of australites and indochinites, representing a large area of the Australasian strewn field, and more recently discovered tektite-like glasses from Central America (Belize) and Western Canada, were carried out. Precise plateau ages were obtained in all cases, yielding indistinguishable ages of 789 ± 9 ka for four australites, 783 ± 5 ka for four indochinites, 783 ± 17 ka for one Western Canadian and 769 ± 16 ka for one Belize impact glass. Concerning major elements and REEs, australites and the Western Canadian impact glass are indistinguishable. If the Western Canadian sample was transported by impact ejection and belongs to the Australasian strewn field, this implies extremely far ballistic transport of 9000 km distance, assuming a source crater in southern Asia. The distinct major element and REE composition of the Belize impact glass suggests formation in another separate impact event. We conclude that the Australasian/Western Canadian impact glasses formed 785 ± 7 ka ago in a single event and Belize impact glass in a separate event 769 ± 16 ka ago. The two impact events forming these two strewn fields occurred remarkably closely related in time, i.e., separated by <30 ka.

  5. Tektite controversy

    International Nuclear Information System (INIS)

    Davis, J.


    Clues as to the possible origin of tektites are found by studying the chemical composition, sites where they are found, and shapes. An important chemical fact of tektites is that they are extremel dry. Tektites lie in four major areas and in three isolated regions. They are distributed as if they fell from the skies. By studying the flanged shapes of the australites, it was concluded that their shape was due to a fast, hot trip through the atmosphere. Tektites show no cosmic ray tracks which implies their space exposure time was short. This rules out the possibility that they are a form of meteorite with these clues in mind, four theories on their possible origin are discussed in this paper. The theories are: (1) terrestial impact by meteorite or comet; (2) lunar impact; (3) terrestial volcanoes; and (4) lunar volcanoes. This article rules out the first three theories for reasons which are given and leans toward the fourth theory as the most probable of the four

  6. Neodymium and strontium isotopic study of Australasian tektites - New constraints on the provenance and age of target materials (United States)

    Blum, Joel D.; Papanastassiou, D. A.; Wasserburg, G. J.; Koeberl, C.


    The Nd and Sr isotopic compositions of Australasian tectites (including two flanged Australian tectites, two low-SiO2 Muong Nong-type tectites, and three high-SiO2 Muong Nong-type tectites) and the Nd, Sm, Sr, and Rb concentrations were investigated by isotope-dilution thermal ionization mass spectrometry, and the Sm-Nd and Rb-Sr isotope systematics were used to study the characteristics of the parental material. It is shown that the Nd and Sr isotopic data provide evidence that all Australasian tektites were derived from a single sedimentary formation with a narrow range of stratigraphic ages close to 170 Ma. It is suggested that all of the Australasian tektites were derived from a single impact event and that the australites represent the upper part of a melt sheet ejected at high velocity, whereas the indochinites represent melts formed at a lower level in the target material distributed closer to the area of the impact.

  7. The chemical durability of tektites - A laboratory study and correlation with long-term corrosion behavior (United States)

    Barkatt, A.; Boulos, M. S.; Barkatt, A.; Sousanpour, W.; Boroomand, M. A.; Macedo, P. B.; Okeefe, J. A.


    Leach tests carried out on tektite specimens (indochinites and australites) under high-dilution conditions show a common behavior characterized by low leach rates (0.00018 g/sq m per d, or 7.2 x 10 to the -12th m/d at 23 C) and an activation energy of (79,600 + or - 700 J/mol). The extent of selective leaching is very small, of the order of 10 to the -8th m. Extrapolation of test results over the lifetime of the tektites gives an excellent agreement with field observations on the extent of corrosion, and this is an important step in establishing the validity of laboratory tests as a basis for the development of models and predictions concerning long-term durabilities at least in the limiting case of high dilution or rapid flow. The results are also shown to be in agreement with various previous observations on the corrosion resistance of tektites. The chemical durability of tektites is observed to be consistent with their composition, highlighting requirements of high corrosion resistance in glasses; these requirements include a silica content in excess of 67 mol percent, an extremely low water content, and an alkali content which is low both absolutely and relative to the di- and poly-valent metal oxide levels. It is shown that artificial glasses which fulfil these criteria are no less corrosion-resistant than the corresponding natural glasses. These conclusions have bearing on the development, as well as on the evaluation, of glasses intended for very long service, such as radioactive waste vitrification media.