The University of Arizona

Geochemistry of drill core samples from Yaxcopoil-1, Chicxulub impact crater, Mexico



The chemical composition of suevites, displaced Cretaceous target rocks, and impactgenerated dikes within these rocks from the Yaxcopoil-1 (Yax-1) drill core, Chicxulub impact crater, Mexico, is reported and compared with the data from the Yucatn 6 (Y6) samples. Within the six suevite subunits of Yax-1, four units with different chemical compositions can be distinguished: a) upper/lower sorted and upper suevite (depth of 795846 m); b) middle suevite (depth of 846861 m); c) brecciated impact melt rock (depth of 861885 m); and d) lower suevite (depth of 885895 m). The suevite sequence (a), (b), and (d) display an increase of the CaO content and a decrease of the silicate basement component from top to bottom. In contrast, the suevite of Y6 shows an inverse trend. The different distances of the Yax-1 and Y6 drilling sites from the crater center (~60, and ~47 km, respectively) lead to different suevite sequences. Within the Cretaceous rocks of Yax-1, a suevitic dike (depth of ~916 m) does not display chemical differences when compared with the suevite, while an impact melt rock dike (depth of ~1348 m) is significantly enriched in immobile elements. A clastic breccia dike (depth of ~1316 m) is dominated by material derived locally from the host rock, while the silicate-rich component is similar to that found in the suevite. Significant enrichments of the K2O content were observed in the Yax-1 suevite and the impact-generated dikes. All impactites of Yax-1 and Y6 are mixtures of a crystalline basement and a carbonate component from the sedimentary cover. An anhydrite component in the impactites is missing (Yax-1) or negligible (Y6).



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