Experimentelle und Analytische Planetologie
Geochemische Untersuchungen an Impaktlithologien des Chicxulub-Kraters, Mexiko
The 65 Ma old Chicxulub impact structure with a diameter of about 180 km is again in the focus of geosciences
because of the successfully drilled scientific well Yaxcopoil-1. Chicxulub is buried beneath thick post-impact
sediments, yet drill core samples of basement lithologies provide a unique insight into age and composition of the
crust beneath Yucatán. This study presents major element, Sr and Nd isotope data for Chicxulub impact
melt lithologies and clasts of basement lithologies in impact breccias from the PEMEX drill cores C-1 and Y-6, as
well as data for ejecta material from the K/T boundaries at La Lajilla, Mexico, and Furlo, Italy. The impact melt
lithologies have an andesitic composition with significantly varying contents of Al, Ca and alkali elements, and a
wide range in Sr and Neodymium isotope compositions. In general, melt lithologies that stayed inside the crater
display less drastic variations than ejected material. The 87Sr/86Sr ratios range from
0.7081 for chloritised spherules from La Lajilla to 0.7151 for sanidine spherules from Furlo. The
143Nd/144Nd ratio is 0.5126 for the La Lajilla, and 0.5120 for the Furlo spherules. In an
Nd-Sr isotope correlation diagram, the melt lithologies plot in a field delimited by Cretaceous platform sediments,
various felsic lithic clasts and a newly found mafic fragment from a suevite. Amongst the fragments from crystalline
basement gneiss, granite and amphibolite have been identified. The Neodymium model ages vary from 0.7 to 1.4 Ga
pointing to different source terraines for these rocks. It follows that the geological evolution and the lithological
composition of the Yucatán basement is obviously more complex than generally assumed, and Gondwanan
as well as Laurentian crust may be present in the Yucatán basement.
Drittmittelgeber:
Beteiligte Wissenschaftler:
Veröffentlichungen:
| 
