^1,2H. M. Sapers, ^1,2,3G. R. Osinski, ^1,2R. L. Flemming, ¹E. Buitenhuis, ¹N. R. Banerjee, ^1,2L. L. Tornabene, ¹S. Blain, ¹J. Hainge
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12796]
¹Department of Earth Sciences, University of Western Ontario, London, Ontario, Canada
²Centre for Planetary Science and Exploration, University of Western Ontario, London, Ontario, Canada
³Department of Physics & Astronomy, University of Western Ontario, London, Ontario, Canada
Published by arrangement with John Wiley & Sons

The ~15 Ma, 26 km diameter Ries impact structure in south-central Germany was one of the first terrestrial impact structures where evidence of impact-associated hydrothermal alteration was recognized. Previous studies suggested that pervasive, high-temperature hydrothermal activity was restricted to the area within the “inner ring” (i.e., the crater-fill impactite units). Here we present mineralogical evidence for localized hydrothermal activity in the ejecta beyond the crater rim in two previously unstudied settings: a pervasively altered lens of suevite ejecta directly overlying the Bunte Breccia at the Aumühle quarry; and suevite ejecta at depth overlain by ~20 m of lacustrine sediments sampled by the Wörnitzostheim 1965 drill core. A comprehensive set of X-ray diffraction analyses indicates five distinct alteration regimes (1) surficial ambient weathering characterized by smectite and a minor illitic component; (2) locally restricted hydrothermal activity characterized by an illitic component and minor smectite; (3) hydrothermal activity at depth characterized by smectite, a minor illitic component, and calcite; (4) hydrothermal activity at depth characterized by smectite, a minor illitic component, calcite, zeolites, and clinochlore; and (5) pervasive hydrothermal activity at depth characterized by smectite, a minor illitic component, and minor clinochlore. These data spatially extend the Ries postimpact hydrothermal system suggesting a much more extensive, complex, and dynamic system than previously thought. Constraining the mineralogical alteration regimes at the Ries impact structure may also further our understanding of impact-associated phyllosilicate formation on Mars with implications for climate models and habitability.