GSA Annual Meeting in Indianapolis, Indiana, USA - 2018

Paper No. 1-14
Presentation Time: 11:15 AM


STOCKLI, Daniel F.1, RASMUSSEN, Cornelia2, ROSS, Catherine3, STOCKLI, Lisa D.4, GULICK, Sean P.S.5, CHATTERJEE, Rudra2, CHRISTESON, Gail L.2, WITTMANN, Axel6, SCHMIEDER, Martin7, KRING, David A.8, XIAO, Long9, MORGAN, Joanna10 and EXPEDITION 364 SCIENCE PARTY, IODP-ICDP3, (1)Geological Sciences, University of Texas at Austin, Austin, TX 78712, (2)Jackson School of Geosciences, Institute for Geophysics, University of Texas at Austin, 10601 Exploration Way, Austin, TX 78758, (3)Jackson School of Geosciences, The University of Texas, Austin, TX 78712, (4)Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78712, (5)University of Texas, Jackson School of Geosciences, Institute for Geophysics and Department of Geological Sciences, J.J. Pickle Research Campus, Bldg. 196, 10100 Burnet Rd., Austin, TX 78758, (6)LeRoy Eyring Center For Solid State Science, Arizona State University, Tempe, AZ 85287, (7)Lunar and Planetary Institute, Houston, TX 77058, (8)NASA Solar System Exploration Research Virtual Institute, Center for Lunar Science and Exploration, Lunar and Planetary Institute, 3600 Bay Area BLVD, Houston, TX 77058, (9)Space Science Institute, Macau University of Science and Technology, Macau, 88972065, China, (10)Earth Science and Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom

IODP-ICDP Expedition 364 drilled the peak ring of the K-Pg Chicxulub impact structure and recovered 580 m of shocked granitic basement. We used zircon U-Pb depth-profile LA-ICP-MS analysis to constrain the pre-impact tectono-magmatic evolution of the impact site at the northern edge of the Yucantan/Maya block, while apatite U-Pb depth-profile LA-ICP-MS and zircon and apatite (U-Th)/He thermochronometry were employed to elucidate the thermal evolution of the granitic basement in the NW portion of the Chicxulub peak ring. These plutonic rocks yielded ~320-350 Ma zircon U-Pb crystallization ages with evidence for earliest Paleozoic inherited zircon cores and Permian zircon rims associated with younger E Mexican arc magmatism. These data document Carboniferous arc magmatism, associated with southward Rheic ocean subduction beneath Yucatan, intruding into peri-Gondwanan Maya block basement (~540 Ma). Detailed LA-ICP-MS depth profiling also revealed that only high-U metamict zircon domains were affected by partial or complete Pb loss attributable to the K-Pg Chicxulub impact. In contrast, apatite U-Pb depth-profiling ages only yielded late Carboniferous ages in response to rapid exhumation associated with post-magmatic cooling or Ouchita orogenic uplift. The apatite U-Pb ages are not reset by the impact and clearly show that the bulk of the felsic rocks in the peak ring were not heated >400C. Zircon (U-Th)/He data for the drilled basement section mostly gave earliest Paleocene ages, clustering around 58-66 Ma, demonstrating impact resetting of the ZHe ages and possible minor age rejuvenation due to post-impact hydrothermal heating. He diffusion experiments on zircon with variable degrees of impact shock microstructures showed ZHe kinetics similar to un-shocked zircons, with the exception of zircon with granular textures. Apatite (U-Th)/He ages range from 15 to 30 Ma and are mostly younger than the impact and likely (partially) reset in response to younger tectonic and deposition events in S Mexico. Together these zircon and apatite U-Pb and (U-Th)/He data from the felsic basement of the Chicxulub in the peak ring allow the reconstruction of its pre-impact tectono-magmatic and thermal evolution, the estimation of the maximum heating during impact (<400C), and post-impact thermal history reconstruction.