Experimental shock metamorphism of terrestrial basalts: Agglutinate-like particle formation,petrology, and magnetism |
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| Authors: | Dmitrii D Badyukov Natalia S Bezaeva Pierre Rochette Jérôme Gattacceca Joshua M Feinberg Myriam Kars Ramon Egli Jouko Raitala Dilyara M Kuzina |
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| Institution: | 1. V.I. Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, 19 Kosygin str., 119991 Moscow, Russia;2. Institute of Physics and Technology, Ural Federal University, 19 Mira Str., 620002 Ekaterinburg, Russia;3. Aix-Marseille Université, CNRS, IRD, Coll. France, CEREGE, 13545 Aix en Provence, France;4. Institute for Rock Magnetism, University of Minnesota, 116 Church Street SE, Minneapolis, Minnesota, 55455 USA;5. Center for Advanced Marine Core Research, Kochi University, B200 Monobe, Nankoku, 783-8502 Japan;6. Central Institute for Meteorology and Geodynamics, Hohe Warte 38, 1190 Vienna, Austria;7. Astronomy Department, University of Oulu, P.O. Box 8. 8000, FI-90014 Oulu, Finland;9. Institute of Geology and Petroleum Technologies, Kazan Federal University, 4/5 Kremlyovskaya Str., 420008 Kazan, Russia |
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| Abstract: | 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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