Résumé
The asteroid impact that resulted in the 66 Myr Chicxulub crater led to the end-Cretaceous mass extinction that eliminated a vast number of species on Earth. The resulting post-impact hydrothermal system likely aided regional ecological rebound and generated a new chemosynthetic habitat in the subsurface. Similar hydrothermal systems may have created habitats on early Earth or other worlds. Hence, there is interest in better understanding the mechanisms, properties, and duration of the Chicxulub hydrothermal system. Using IODP-ICDP Expedition 364 drill core, porosity and permeability measurements have been acquired for the first time from the peak ring (ring of hills generated in large impacts surrounding a crater's central melt sheet). These data show that the suevite (melt bearing impact breccia) has permeabilities ranging from approximately 1x10 (super -4) mD to 1.2x10 (super -1) mD which are lower than previously assumed. Permeability of the peak ring granite is approximately 9.8x10 (super -1) mD, higher than the overlying suevite and melt sheet ( approximately 7x10 (super -4) mD). These physical properties prescribed to high fidelity layers, imaged in full waveform seismic data, provide the basis for the development of a new hydrothermal convection model within the crater. Preliminary model results show convection was concentrated within the peak ring granite. This convection is due to higher permeability which provides more efficient pathways for fluid flow as well as the granite's proximity to the melt sheet which supplies heat to the system. Modeled fluid stream-lines indicate that ambient pore water was circulated within the system via lateral inflow from distances up to several tens of km beneath the melt sheet and sourced from the collapsed transient crater rim including Cretaceous carbonates and evaporites. Interaction with this preexisting groundwater can affect the evolution of the hydrothermal system along with the structure of the subsurface and chemistry of the system. We investigate boundary conditions and the role of latent heat on the longevity of the system, to compare with thermochronologic results from Exp. 364. Understanding its progression and development can provide insight into the Chicxulub hydrothermal habitat and subsequently provide a framework for the study of similar physical properties possibly providing habitats on other planetary bodies.