Other
Scientific paper
Nov 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000m%26ps...35.1229k&link_type=abstract
Meteoritics & Planetary Science, vol. 35, no. 6, pp. 1229-1238 (2000).
Other
22
Scientific paper
The 65 Ma Chicxulub impact structure, Mexico, with a diameter of about 180 km is in the focus of geoscientific research because of it's link to the mass extinction event at the Cretaceous-Tertiary (K/T) boundary. Chicxulub, now buried beneath thick post-impact sediments is most probably one of the best preserved terrestrial impact structures known. Because of it's in-accessibility, only limited samples on the impact lithologies from a few drill cores are available. We report major element, and Sr, Nd, O, and C isotope data for Chicxulub impact melt lithologies and basement clasts in impact breccias of drill cores C-1, and Y-6, and for melt particles in the Chicxulub ejecta horizon at the K/T boundary in Beloc, Haiti. The melt lithologies with SiO2 ranging from 58 to about 63 wt% show significant variations in the content of aluminum, calcium, and the alkalies. In the melt matrix samples, ?13C of the calcite is about -3 deg. The ?18O values for the siliceous melt matrices of Y-6 samples range from 9.9. to 12.4 deg. Melt lithologies and the black Haitian glass have rather uniform 87Sr/86Sr ratios (0.7079 to 0.7094); only one lithic fragment displays 87Sr/86Sr of 0.7141. The Sr model ages TSrUR for most lithologies range from 830 to 1833 Ma; unrealistic negative model ages point to an open Rb-Sr system with loss of Rb in a hydrothermal process. The 143Nd/144Nd ratios for all samples, except one basement clast with 143Nd/144Nd of 0.5121, cluster at 0.5123 to 0.5124. In an ?Nd-?Sr-diagram, impactites plot in a field delimited by ?Nd of -2 to -6, and ?Sr of 55 to 69. This field is not defined by the basement lithologies described to occur as lithic clasts in impact breccias and Cretaceous sediments. At least one additional intermediate to mafic pre-cursor component is required to explain the data.
Agrinier Pierre
Deutsch Alexander
Kettrup Bianca
Ostermann Markus
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