Microbial Sulfur Isotope Fractionation in the Chicxulub Hydrothermal System.

Target lithologies and post-impact hydrothermal mineral assemblages in a new 1.3 km deep core from the peak ring of the Chicxulub impact crater indicate sulfate reduction was a potential energy source for a microbial ecosystem (Kring 2020). That sulfate was metabolized is confirmed here by microscopic pyrite framboids with δS values of -5 to -35 ‰ and ΔS values between pyrite and source sulfate of 25 to 54 ‰, which are indicative of biologic fractionation rather than inorganic fractionation processes. These data indicate the Chicxulub impact crater and its hydrothermal system hosted a subsurface microbial community in porous permeable niches within the crater's peak ring.