Impact craters have their magnetizations reduced by impact plasma shielding

0560677 - GLÚ 2023 RIV HR eng A - Abstract
Kletetschka, Günther - Takac, M. - Karimi, K. - Kavková, R. - Ucar, H.
Impact craters have their magnetizations reduced by impact plasma shielding.
17th “Castle Meeting” on Palaeo, Rock and Environmental Magnetism. Zagreb: Ruđer Bošković Institute, 2022 - (Frančišković-Bilinski, S.; Böhnel, H.; Egli, R.; Hirt, A.; Petrovský, E.; Spassov, S.; Werner, T.). s. 66-66. ISBN 978-953-7941-44-4.
[Castle Meeting New Trends on Paleo, Rock and Environmental Magnetism /17./. 28.08.2022-03.09.2022, Trakošćan]
Institutional support: RVO:67985831
Keywords : Impact cratering * Magnetic remanence * Magnetic anomalies * shock detection * Acraman and Santa Fe craters
OECD category: Geology
https://castle2020.irb.hr/Program-and-Book-of-Abstracts

The shock exposure of both the Santa Fe’s impact structure in New Mexico and Acraman impact crater in south Australia is evidenced by shatter cones. We detected a magnetic mechanism revealing a plasma’s presence during the impact processes. Rocks before the impacts were once magnetized by a geomagnetic field. An observed remanent magnetization of the shocked rocks was more than an order of magnitude lower than rocks formed in the presence of geomagnetic field. It was suggested that the impact generated plasma can generate magnetic shielding during the time scale that is comparable to the time when shock wave propagate through the rocks under the impact crater (Kletetschka et al, 2021). The incoming shock wave destabilizes the magnetic grains, so they are in a superparamagnetic-like state during the shock’s exposure. The shielding of the ambient magnetic field prevents alignment of the magnetic vectors, leaving the individual magnetized grains in random orientations, and thus significantly lowering the overall magnetic intensity. Our data not only clarify how an impact process allows for a reduction of magnetic remanence but also inspire a new direction of effort to study impact sites, using paleointensity reduction as a new impact proxy.

Permanent Link: https://hdl.handle.net/11104/0333973