Experimentelle und Analytische Planetologie
Geochemische Untersuchungen an Impaktlithologien des Popigai-Kraters, Russland
It has been demonstrated convincingly that geochemical and isotopic characteristics of impact melt lithologies (melt
rocks, melt particles in melt breccias and suevites) can be used to constrain their precursor materials, and to relate
ejected impact melt glass in proximal and distant ejecta to the respective source crater. An unambiguous correlation
of ejected impact melt products (tektites, micro-tektites, impact melt glass, micro-crystites) with the parent crater,
however, was only possible in a few cases despite the high sensitivity of isotopic techniques. This may be due to the
fact that only parts of the terrestrial crater population are known but also due to the lack of systematic isotope
studies on impact craters: Melt products of one cratering event may display more heterogeneous isotope
characteristics than hitherto assumed. The 35.7 ± 0.2 Ma old Popigai crater, Siberia, with a diameter of
about 100 km is one of the best preserved terrestrial impact structures. The heterogeneous target at the Popigai
impact site comprises Archean to Proterozoic metamorphic rocks of the crystalline basement, Proterozoic red beds,
and Cambrian to Cretaceous clastic sediments and sedimentary rocks, amongst them carbonate rocks. Moreover,
Proterozoic and Permo-Triassic dolerite dykes are found in the target. Based on major element, Sr, and Nd isotope
data for these target rocks as well as for various types of impactites, we show that the melt layer reflects the
precursor lithologies in the respective crater sectors. Moreover, we provide the first solid evidence for the clear
relation of microtektites and microkrystites in the Upper Eocene ejecta layer to the Popigai event.
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