Fachbereich 14 - Geowissenschaften
Institut für Planetologie
Analytische Planetologie

Geochemische Untersuchungen an Impaktlithologien des Popigai-Kraters, Russlnd

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 th erespective 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.

Drittmittelgeber:

Deutsche Forschungsgemeinschaft

Beteiligte Wissenschaftler:

Deutsch, A. (Leiter), Kettrup, B., Masaitis, V. L. (Karpinsky Institute, St. Petersburg)

Veröffentlichungen:

Kettrup, B., Deutsch, A., Masaitis, V.L. (2003): Homogeneous impact melts produced by a heterogeneous target? Sr-Nd isotopic evidence from the Popigai crater, Russia. Geochim. Cosmochim. Acta 67, 733-750.