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  • 1
    Publication Date: 2013-08-31
    Description: The Cretaceous/Tertiary (K/T) boundary Chicxulub impact is the best preserved large impact in the geologic record. The Chicxulub crater has been buried with no apparent erosion of its intracrater deposits, and its ejecta blanket is known and is well preserved at hundreds of localities globally. Although most of the molten material ejected from the crater has been largely altered, a few localities still preserve tektite glass. Availability of intra- and extracrater impact products as well as plausible matches to the targeted rocks allows the comparison of compositions of the different classes of impact products to those of the impacted lithologies. Determination of trace-element compositions of the K/T tektites, Chicxulub melt rock, and the targeted Yucatan silicate basement and carbonate/evaporite lithologies have been made using instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-MS). Some sample splits were studied with both techniques to ensure that inter-laboratory variation was not significant or could be corrected. The concentration of a few major and minor elements was also checked against microprobe results. Radiochemical neutron activation analysis (RNAA) was used to determine Ir abundances in some samples.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 2: G-M; p 657-658
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  • 2
    Publication Date: 2019-08-14
    Description: Ruthenium (Ru) and iridium (Ir) are the least mobile platinum group elements (PGE's) within the Cretaceous-Tertiary (K-T) boundary clay (BC). The Ru/Ir ratio is, therefore, the most useful PGE interelement ratio for distinguishing terrestrial and extraterrestrial contributions to the BC. The Ru/Ir ratio of marine K-T sections (1.77 +/- 0.53) is statistically different from that of the continental sections (0.93 +/- 0.28). The marine Ru/Ir ratios are chondritic (C1 = 1.48 +/- 0.09), but the continental ratios are not. We discovered an inverse correlation of shocked quartz size (or distance from the impact site) and Ru/Ir ratio. This correlation may arise from the difference in Ru and Ir vaporization temperature and/or fractionation during condensation from the ejecta cloud. Postsedimentary alteration, remobilization, or terrestrial PGE input may be responsible for the Ru/Ir ratio variations within the groups of marine and continental sites studied. The marine ratios could also be attained if approximately 15 percent of the boundary metals were contributed by Deccan Trap emissions. However, volcanic emissions could not have been the principal source of the PGE's in the BC because mantle PGE ratios and abundances are inconsistent with those measured in the clay. The Ru/Ir values for pristine Tertiary mantle xenoliths (2.6 +/- 0.48), picrites (4.1 +/- 1.8), and Deccan Trap basalt (3.42 +/- 1.96) are all statistically distinct from those measured in the K-T BC.
    Keywords: GEOPHYSICS
    Type: Lunar and Planetary Inst., International Conference on Large Meteorite Impacts and Planetary Evolution; p 25
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  • 3
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    Texas A & M University
    In:  Proceedings of the Ocean Drilling Program: Scientific Results, 158 . pp. 27-40.
    Publication Date: 2020-06-08
    Description: Representative samples of drill core were collected from each of the five main areas drilled on the TAG (Trans-Atlantic Geotraverse) mound during Leg 158 (Humphris, Herzig, Miller, et al., 1996). In this report, we present the results of chemical analyses of 66 samples previously analyzed for Cu, Fe, Zn, Pb, Ag, and Cd by atomic absorption during Leg 158. Data are presented for an additional 38 elements plus total sulfur, loss on ignition, and the rare earth elements by a combination of optical emission spectrometry (ICP-ES), mass spectrometry (ICP-MS), and neutron activation (INAA). These data are discussed in detail in other chapters in this volume.
    Type: Article , PeerReviewed
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