Experimental shock metamorphism of terrestrial basalts: Agglutinate-like particle formation, petrology, and magnetism

1Dimitri D. Badyukov,2,3Natalia S. Bezaeva,4Pierre Rochette,4Jérôme Gattacceca,5Joshua M. Feinberg,6Myriam Kars,7Ramon Egli,8Jouko Raitala,9Dilyara M. Kuzina
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.13006]
1V.I. Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, Russia
2Institute of Physics and Technology, Ural Federal University, Ekaterinburg, Russia
3Institute of Geology and Petroleum Technologies, Kazan Federal University, Kazan, Russia
4Aix-Marseille Université, CNRS, IRD, Coll. France, CEREGE, Aix en Provence, France
5Institute for Rock Magnetism, University of Minnesota, Minneapolis, Minnesota, USA
6Center for Advanced Marine Core Research, Kochi University, Nankoku, Japan
7Central Institute for Meteorology and Geodynamics, Vienna, Austria
8Astronomy Department, University of Oulu, Oulu, Finland
9Institute of Geology and Petroleum Technologies, Kazan Federal University, Kazan, Russia
Published by arrangement with John Wiley & Sons

Hypervelocity impacts occur on bodies throughout our solar system, and play an important role in altering the mineralogy, texture, and magnetic properties in target rocks at nanometer to planetary scales. Here we present the results of hypervelocity impact experiments conducted using a two-stage light-gas gun with 5 mm spherical copper projectiles accelerated toward basalt targets with ~6 km s−1 impact velocities. Four different types of magnetite- and titanomagnetite-bearing basalts were used as targets for seven independent experiments. These laboratory impacts resulted in the formation of agglutinate-like particles similar in texture to lunar agglutinates, which are an important fraction of lunar soil. Materials recovered from the impacts were examined using a suite of complementary techniques, including optical and scanning electron microscopy, micro-Raman spectroscopy, and high- and low-temperature magnetometry, to investigate the texture, chemistry, and magnetic properties of newly formed agglutinate-like particles and were compared to unshocked basaltic parent materials. The use of Cu-projectiles, rather than Fe- and Ni-projectiles, avoids magnetic contamination in the final shock products and enables a clearer view of the magnetic properties of impact-generated agglutinates. Agglutinate-like particles show shock features, such as melting and planar deformation features, and demonstrate shock-induced magnetic hardening (two- to seven-fold increases in the coercivity of remanence Bcr compared to the initial target materials) and decreases in low-field magnetic susceptibility and saturation magnetization.

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