Cubic zirconia in >2370 °C impact melt records Earth’s hottest crust

1Nicholas E. Timms, 1Timmons M. Erickson, 2Michael R. Zanetti, 3Mark A. Pearce, 4Cyril Cayron, 1,5Aaron J. Cavosie, 1Steven M. Reddy, 6Axel Wittmann, 7Paul K. Carpenter
Earth and Planetary Science Letters 477, 52-58 Link to Article [https://doi.org/10.1016/j.epsl.2017.08.012]
1Department of Applied Geology, Curtin University, Perth, GPO Box U1987, Western Australia 6845, Australia
2University of Western Ontario, 1151 Richmond St, London, Ontario, N6A 3K7 Canada
3CSIRO Mineral Resources, Australian Resources Research Centre, 26 Dick Perry Avenue, Kensington, WA 6151, Australia
4Laboratory of ThermoMechanical Metallurgy (LMTM), PX Group Chair, École Polytechnique Fédérale de Lausanne (EPFL), Rue de la Maladière 71b, 2000 Neuchâtel, Switzerland
5NASA Astrobiology Institute, Department of Geoscience, University of Wisconsin–Madison, Madison WI, USA
6LeRoy Eyring Center for Solid State Science, Arizona State University, 901 S Palm Walk, Tempe, AZ, 85287, USA
7Washington University in St Louis, Earth and Planetary Science Department and the McDonnell Center for Space Sciences; 1 Brookings Drive, St Louis MO, 63112, USA
Copyright Elsevier

Bolide impacts influence primordial evolution of planetary bodies because they can cause instantaneous melting and vaporization of both crust and impactors. Temperatures reached by impact-generated silicate melts are unknown because meteorite impacts are ephemeral, and established mineral and rock thermometers have limited temperature ranges. Consequently, impact melt temperatures in global bombardment models of the early Earth and Moon are poorly constrained, and may not accurately predict the survival, stabilization, geochemical evolution and cooling of early crustal materials. Here we show geological evidence for the transformation of zircon to cubic zirconia plus silica in impact melt from the 28 km diameter Mistastin Lake crater, Canada, which requires super-heating in excess of 2370 °C. This new temperature determination is the highest recorded from any crustal rock. Our phase heritage approach extends the thermometry range for impact melts by several hundred degrees, more closely bridging the gap between nature and theory. Profusion of >2370 °C superheated impact melt during high intensity bombardment of Hadean Earth likely facilitated consumption of early-formed crustal rocks and minerals, widespread volatilization of various species, including hydrates, and formation of dry, rigid, refractory crust.

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