Numerical modeling of impact‐induced hydrothermal activity at the Chicxulub crater

Abstract

Abstract-Large impact events like the one that formed the Chicxulub crater deliver significant amounts of heat that subsequently drive hydrothermal activity. We report on numerical modeling of Chicxulub crater cooling with and without the presence of water. The model inputs are constrained by data from borehole samples and seismic, magnetic, and gravity surveys. Model results indicate that initial hydrothermal activity was concentrated beneath the annular trough as well as in the permeable breccias overlying the melt. As the system evolved, the melt gradually cooled and became permeable, shifting the bulk of the hydrothermal activity to the center of the crater. The temperatures and fluxes of fluid and vapor derived from the model are consistent with alteration patterns observed in the available borehole samples. The lifetime of the hydrothermal system ranges from 1.5 to 2.3 Myr depending on assumed permeability. The long lifetimes are due to conduction being the dominant mechanism of heat transport in most of the crater, and significant amounts of heat being delivered to the near-surface by hydrothermal upwellings. The long duration of the hydrothermal system at Chicxulub should have provided ample time for colonization by thermophiles and/or hyperthermophiles. Because habitable conditions should have persisted for longer time in the central regions of the crater than on the periphery, a search for prospective biomarkers is most likely to be fruitful in samples from that region.

Volume 364: Chicxulub: Drilling the K-Pg Impact Crater

“…Of interest will be nannoplankton recovery at "ground zero" in comparison to the global response (e.g., Jiang et al, 2010). It is possible that a long-term, impact-initiated hydrothermal circulation system (Abramov and Kring, 2007) caused a delay in local recovery. Did diversity gradually recover with the hardiest taxa appearing first and new species slowly populating the basin as they originated, as in other global sections, or did the whole assemblage return simultaneously once the environment stabilized?…”

“…We will use cores from the post-impact sedimentary rocks to examine the recolonization of the ocean, including what biota came back first (benthic versus planktic, phytoplankton versus Figure F7. Numerical modeling of a hydrothermal system through a peak ring in a large impact structure (redrawn from Abramov and Kring, 2007). zooplankton, specialists versus generalists), how long it took to return to normal conditions compared to other localities outside the crater, and whether cold-water species occur in the crater, indicating severe cooling due to post-impact environmental change (e.g., Vellekoop et al, 2014).…”

“…Was hydrothermal circulation focused in specific zones, as it was in Hole Yax-1 (along faults and lithologic contacts), or was it more pervasive? Wireline logs and petrophysical measurements on the core will be used to measure fracture density and porosity, which will help assess ancient permeability-an important parameter in modeling hydrothermal systems (Abramov and Kring, 2007).…”

Impact‐Induced Hydrothermal Activity

“…Large peak-ring structures will comprise a number of different heat sources, resulting in the development of several independent convection cells, initially in the annular trough, in breccias above the central melt sheet and in the fractured modification zone and likely in the peak-ring area and, then, after solidification and cooling of the melt sheet, in the central uplift area (e.g. Abramov and Kring, 2007). In smaller structures a simple convective cell Jõeleht et al (2005) and Abramov and Kring (2007).…”

“…Abramov and Kring, 2007). In smaller structures a simple convective cell Jõeleht et al (2005) and Abramov and Kring (2007). (See Colour Plate 18) system in the most heated central part of the crater will typically develop (e.g.…”