Shock‐induced formation of wüstite and fayalite in a magnetite‐quartz target rock

1,2Leonard F. Henrichs,2Agnes Kontny,2Boris Reznik,3Uta Gerhards,4Jörg Göttlicher,2Tim Genssle,2Frank Schilling
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13422]
1Karlsruhe Institute of Technology, Institute of Nanotechnology, Hermann‐von‐Helmholtz‐Platz 1, 76344 Eggenstein‐Leopoldshafen, Germany
2Karlsruhe Institute of Technology, Institute of Applied Geosciences, Adenauerring 20, 76131 Karlsruhe, Germany
3Karlsruhe Institute of Technology, Institute for Micro Process Engineering, Hermann‐von‐Helmholtz‐Platz 1, 76344 Eggenstein‐Leopoldshafen, Germany
4Karlsruhe Institute of Technology, Institute for Photon Science and Synchrotron Radiation (IPS), Hermann‐von‐Helmholtz‐Platz 1, 76344 Eggenstein‐Leopoldshafen, Germany
Published by arrangement with John Wiley & Sons

Projectile–target interactions as a result of a large bolide impact are important issues, as abundant extraterrestrial material has been delivered to the Earth throughout its history. Here, we report results of shock‐recovery experiments with a magnetite‐quartz target rock positioned in an ARMCO iron container. Petrography, synchrotron‐assisted X‐ray powder diffraction, and micro‐chemical analysis confirm the appearance of wüstite, fayalite, and iron in targets subjected to 30 GPa. The newly formed mineral phases occur along shock veins and melt pockets within the magnetite‐quartz aggregates, as well as along intergranular fractures. We suggest that iron melt formed locally at the contact between ARMCO container and target, and intruded the sample causing melt corrosion at the rims of intensely fractured magnetite and quartz. The strongly reducing iron melt, in the form of μm‐sized droplets, caused mainly a diffusion rim of wüstite with minor melt corrosion around magnetite. In contact with quartz, iron reacted to form an iron‐enriched silicate melt, from which fayalite crystallized rapidly as dendritic grains. The temperatures required for these transformations are estimated between 1200 and 1600 °C, indicating extreme local temperature spikes during the 30 GPa shock pressure experiments.

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