Podrobnosti záznamu

Název
    Tektite origin by hypervelocity asteroidal or cometary impact: Target rocks, source craters, and mechanisms
Údaj o odpovědnosti
    Christian Koeberl
Další názvy
    Large Meteorite Impacts and Planetary Evolution (Variant.)
Autor
    Koeberl, Christian
Jazyk
    anglicky
Zdrojový dokument - seriál
    Geological society of America special paper
Svazek/č.
    Vol. 293
Strany
    p. 133-151
Rok
    1994
Poznámky
    2 obr., 3 tab., 1 fot., 5 s.bibl.
    il.
    Zkr. název ser.: Geol. Soc. Amer. spec. Pap.
Předmětová skupina
    geochemie izotopická
    geochronologie
    kráter impaktní
    metamorfóza šoková
    moldavit
    sklo přírodní
    tektity
    volatilizace
    vzácné zeminy
Geografické jméno
    Asie jihovýchodní
    Austrálie
    Česká republika
    Pobřeží slonoviny
    Rakousko
    SRN
    USA
Klíčové slovo
    Asteroidal
    Cometary
    Craters
    Hypervelocity
    Impact
    Mechanisms
    Origin
    Rocks
    Source
    Target
    Tektite
Abstrakt (anglicky)
   Tektites are natural glasses that occur on earth in four distinct strewn fields (North American, Central European, Ivory Coast, and Australasian). Geochemical arguments have shown that tektites have been derived by hypervelocity impact melting from terrestrial upper crustal rocks, most likely sediments. The contents of Be-10 in tektites are evidence for a derivation of tektites from surface rocks, thus precluding an origin from greater depth in the crater. For two of the four tektite strewn fields (Ivory Coast, Central European), a possible connection to impact craters (Bosumtwi, and Ries, respectively) has been suggested on the basis of chemical, isotopic, and age data. No clear crater identifications have been made for the North American or Australasian strewn fields, although there are good candidates for both.
   Even though the geochemistry of tektites is in unequivocal favor of an origin by impact melting of terrestrial rocks, the unambiguous demonstration of the presence of an extraterrestrial contribution to the chemistry of tektites remains a problem. However, recent osmium isotope studies have shown that there is a clear meteoritic signature in at least some tektites. The exact mechanism of tektite formation is still not obvious, although some facts become increasingly clear. Tektite production is still not obvious, although some facts become increasingly clear. Tektite production is still not obvious, although some facts become increasingly clear. Tektite production requires specific impact conditions - otherwise there would be many more tektite strewn fields connected to the 150 or so known impact craters.
   Tektites are produced by nonequilibrium shock melting of surficial rocks, and the superheated melt may be subjected to a plasma phase during which they are subjected to partial reduction. They are then lofted though the atmosphere (probably in the wake of the expanding vapor cloud) quenched, and distributed over a geographically extended area - the strewn field
Přispěvatel
    Česká geologická služba
Kód přispěvatele
    ČGS (UNM)
Zdrojový formát
    U
Datum vložení
    17. 8. 2007
Datum importu
    8. 8. 2012