Hot rocks: Constraining the thermal conditions of the Mistastin Lake impact melt deposits using zircon grain microstructures

The production of superheated melt during hypervelocity impact events has been proposed to be a common occurrence on terrestrial planetary bodies. Recent direct evidence temperatures exceeding >2370°C from the Kamestastin (Mistastin Lake) structure, Canada, was based single glass sample. Such high have strong implications for evolution crustal material, thermal history cratering events, and rheology melt. However, although widely predicted in previous studies, with exception Mistastin Lake glass, there is little multiple settings across an structure. Therefore, outstanding question how heterogeneous are conditions In this work, we analyze crystallographic orientations microstructures zircon grains precursor parent phases baddeleyite crystals, four different samples representing entire melt-bearing stratigraphy at Mistastin: vesicular clast-poor rock, clast-rich glass-bearing breccia. Using electron microprobe analysis followed by backscatter diffraction, discovered that vermicular coronae crystals contain cubic zirconia precursor, indicative temperature >2370°C. We also report superheating up 1673°C addition, first high-pressure polymorph reidite former granular neoblastic (FRIGN) breccia, implying minimum peak shocks 30–40 GPa. identification two localities demonstrates (1) not restricted solely rapidly cooled rock therefore more distributed structures, (2) can investigate P-T pathways settings, providing clearer picture