^1,2*Craig R. Walton, ³Mahesh Anand, and ¹Maria Schönbächler
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14333]
¹Department of Earth Sciences, Institute f€ur Geochemie und Petrologie, ETH Zurich, Zurich, Switzerland
²Institute of Astronomy, University of Cambridge, Cambridge, UK
³School of Physical Sciences, Open University, Milton Keynes, UK
Published by arrangement with John Wiley & Sons

The majority of ordinary chondrite (OC) meteorites record some amount of textural evidence for impact-induced deformation. Melt veins in some shocked samples have been compared to terrestrial impact-related pseudotachylites, which form by frictional melting of host rock. However, lacking in situ context, the role of friction in driving impact-related melting in meteorites remains unclear. Here, we present evidence for an important role for shear deformation and friction in complementing shock melting of OC material. We find microfaults directly associated with textural evidence for quenched frictional shock melt in samples of a broad range of bulk shock stages and across all three classes studied (LL, L, or H). Microfaults occur in 20% of our studied samples. We identify examples of both individual microfaults and, in rare cases, microfault networks, complete with subsidiary shear structures. Our observations indicate that friction plays an important role in melt generation in weakly to moderately shocked samples and may also be relevant for strongly shocked meteorites. Microfault structures may be of underestimated significance in chondrites in general—both with regard to their general abundance and their possible utility for elucidating the geological settings sampled by meteoritic impactites.

¹Christina M. Verhagen et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14331]
¹Department of Earth and Planetary Sciences, Rutgers University, Piscataway Township, New Jersey, USA
Published by arrangement with John Wiley & Sons

Large terrestrial impacts may produce vast subsurface hydrothermal systems, capable of generating conditions favorable to the origin of life. Modeling suggests that these systems may persist for >1 million years for basin-sized craters; however, direct experimental constraints on hydrothermal system duration are needed. Paleomagnetism may be used as a tool to study the nature and duration of the postimpact hydrothermal system generated within the upper peak ring of the 200 km diameter Chicxulub crater (Yucatán Peninsula, México). Previous work observed that upper peak ring suevite samples contained characteristic remanent magnetizations with negative and positive inclinations, with most samples having a magnetic inclination close to −44°, the expected paleoinclination at the crater at the time of the impact. This magnetic record was at the time interpreted as chemical remanent magnetization (CRM) acquired over a period of at least 150 thousand years, from the time of the impact in geomagnetic Chron C29r into Chron C29n. We conducted further paleomagnetic and rock magnetic studies of upper peak ring rocks and found that, while most samples likely contain CRM acquired during Chron C29r, the dispersion of magnetic inclinations within suevite subunits is more likely attributed to pre-depositional remanence held within clasts than the recording of magnetic reversals. Therefore, the paleomagnetic record of the peak ring suevites is non-ideal for inferring the duration of the Chicxulub postimpact hydrothermal system.