HR: 1330h
AN: P52A-0479    [PDF]
TI: Geochemistry of K/T-boundary Chicxulub ejecta of NE-Mexico
AU: * Harting, M
EM: markus.harting@img.uni-karlsruhe.de
AF: Institute of Mineralogy and Geochemistry, Karlsruhe University, Fritz-Haber Weg, Karlsruhe, 76131 Germany
AU: Deutsch, A
EM: deutsca@uni-muenster.de
AF: Institut fuer Planetologie, Univ. of Muenster, Wilhelm-Klemm-Str. 10, Muenster, 48149 Germany
AU: Rickers, K
EM: karen.rickers@desy.de
AF: HASYLAB, DESY, Notkestraįe 85, Hamburg, 22603 Germany
AB: Many K/T sections all over the world contain impact spherules supposed related to the Chicxulub event. This study focus on ejecta layers in NE-Mexican profiles. We carried out systematic XRF and synchrotron radiation measurements on such spherules at the HASYLAB and ANKA facilities as well as microprobe analyses (CAMECA SX50). Area scans on tektite-like material of the Bochil section reveal a pronounced zonation in the inner part, dominated by Ba and Sr whereas secondary CaCO3 dominates in the altered margin. The composition of the spherules from the Mesa-Juan Perez section differ significantly from the Beloc (Haiti) and Bochil tektite glasses. At Mesa-Juan Perez, spherules are either extremely rich in Fe and Ca or consist of smectite, some of those carry carbonate inclusions. Yttrium, La and Ce are zoned within the smectite with concentrations below the detection limit and up to 20 ęg/g The Ca-rich inclusions are enriched in Y (up to 35 ęg/g) and La (18 ęg/g) and, compared to the surrounding smectite, also in Ce (up to 34 ęg/g). The Ce enrichment in spherules from the Mesa-Juan Perez section indicates impact-melted carbonates of the Yucatan carbonate platform as possible precursor rocks. Recent investigations focus on the chemistry of melt rock samples from the PEMEX wells Yucatan-6 and Chicxulub-1: Their average composition (mean of 250 data points in wt-percent ) is 61.6 for SiO2, 0.16 for TiO2, 18.07 for Al2O3, 0.01 for Cr2O3, 1.98 for Na2O, 1.5 for FeO, 0.05 for MnO, 0.01 for NiO, 0.31 for MgO, 9.14 for K2O, 3.44 for CaO, and 0.01 for SO2. These results are in some cases comparable to the geochemistry of ejecta glasses, e.g. from Beloc (Haiti).
UR: http://www.uni-karlsruhe.de/~img/seite_489.html
DE: 1065 Trace elements (3670)
DE: 1630 Impact phenomena
DE: 5420 Impact phenomena (includes cratering)
DE: 5494 Instruments and techniques
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting