Constraints for Modeling Chemical Transport during Hydrothermal Alteration in Large and Small Impact Craters

Introduction: Modeling of hydrothermal alteration has progressed greatly in recent years. One of the next challenges for modeling is to explain the observations of elemental transport observed in terrestrial impact craters. We present data from our work that illustrates some of the evidence for impact craters of different sizes. For the large, 180-200 km diameter, Chicxulub impact crater, data from the Yaxcopoil 1 drill core suggests that some chemical transport has occurred, especially for Li, B, and Be. In contrast, for the small 1.8 km diameter Lonar crater, very little evidence for chemical mobility has been found. Extrapolation models to other planetary bodies, such as Mars, will require an appreciation of the differences in fluid composition.