Logoisk impact structure, Belarus: Shock transformation of zircon

Abstract

The 17 km diameter, 30 Ma old Logoisk structure in Belarus (54°12′ N, 27°48′ E) was intensively drilled within the crater area. We summarize geological structure and petrologic information previously published mostly in Russian and describe shock deformation of zircon for the first time. The shock deformation features of zircon in the Logoisk suevite include the transition to reidite, the formation of planar fractures and granular textures, and the thermal decomposition to ZrO2 and SiO2. The presence of reidite in two grains in suevite was confirmed by micro‐Raman spectroscopy and EBSD (electron backscattered diffraction). Reidite was found in suevite glass of the Logoisk structure in grains containing zircon and in the ZrO2‐enriched rims on zircon. Granular zircon is commonly associated with ZrO2 and occurs as rims on zircon with interstitial impact melt, as dendritic rims, and in the inner parts of a zircon grain. A granular zircon from Logoisk represents the highest documented temperature of zircon transformation. The new data expands the knowledge of the P‐T conditions of formation of the Logoisk structure.