Résumé
We present modeling results and an update to our permeability measurements on 1-inch (25.4 mm) core plugs from the Chicxulub peak ring obtained from International Ocean Discovery Program/International Continental Scientific Drilling Program Expedition 364. This project is a joint study between the University of Texas at Austin (UT) and Stanford University. Steady-state permeability measurements at UT used deionized water and brine, while Stanford used Nitrogen gas with the pulse-decay method. Both studies used multiple confining stress conditions (10 to 26 MPa) in four loading cycles while maintaining constant pore pressure. At UT Austin, we measured nine core plugs from 5 different lithologies in the core: 4 medium-grained suevite samples from core Unit 2A, a coarse- grained suevite sample from Unit 2B, impact melt rock from Unit 3, 2 granite samples from Unit 4, and a dolerite sample from Unit 4. All samples were micro-CT scanned at 20 mu m voxel resolution before and after permeability testing. The permeability for the medium grained suevite samples ranged from 3.6 x 10 (super -16 ) m (super 2) - 1.0 x 10 (super -17 ) m (super 2) (0.36-0.01 mD) and approximately 1.0x10 (super -15) m (super 2) ( approximately 1 mD) for the granitoid samples. The melt rock and coarse-grained suevite were significantly less permeable, with values of less than 10 (super -18) m (super 2) ( approximately 1 mu D). The dolerite sample was almost impermeable, with values in the nano-Darcy range or below. We use the UT Austin and Stanford permeability results, as well as results from an additional study from Montpellier University, as inputs for hydrothermal modeling using COMSOL. The starting thermal state is based on iSALE modeling (courtesy of Imperial College) of conditions after the crater modification stage of impact. We explore the implications of the orders of magnitude contrast in permeability between the granite and the suevite and melt rock for the lifespan of the post-impact hydrothermal system and structure. The low permeability values of the suevite and melt rock may have acted as an aquitard, restricting flow between the granite and the ocean, and the low permeability diorite within the granite may have produced isolated flows within the granite as well.