U–Pb geochronology of apatite and zircon from the Brent impact structure, Canada: a Late Ordovician Sandbian–Katian boundary event associated with L-Chondrite parent body disruption

U‐Pb dating of zircon and monazite from the uplifted Variscan crystalline basement of the Ries impact crater

“…These metamict grains could have first been reset during the approximately 15 Ma Ries impact event, followed by a later postimpact Pb loss event; however, such a scenario cannot be proven from the data. A complex interplay of postimpact Pb loss and common Pb addition would be similar to observations made by McGregor et al (2020) for some shocked zircon from impact melt rocks in the Brent impact structure.…”

“…Discordance in zircon typically results from (1) incorporation of common Pb, (2) Pb loss, (3) U gain, and/or (4) mixing of different age domains in analyzed volumes. The U‐Pb system in zircon grains that have been exposed to impacts is often reset to the age of the impact events as a result of Pb loss from recrystallized and/or porous domains, which are then more susceptible to suffer postimpact Pb loss due to the small diffusion domain size of granular zircon (e.g., McGregor et al, 2020; Schmieder et al, 2015). Modern Pb loss can also affect metamict zircon domains without the need to invoke an impact event (e.g., Nasdala et al, 1998).…”

“…2 of Schmieder & Kring, 2020), despite the great potential of zircon to also provide constraints on P – T conditions during impact (e.g., Erickson et al, 2016; Gucsik, Koeberl, et al, 2004; Gucsik, Zhang, et al, 2004; Timms et al, 2017; Wittmann et al, 2006). Zircon (ZrSiO 4 ) U‐Pb dating has been successfully applied to date the 2229 ± 5 Ma Yarrabubba impact structure in Australia (impact‐generated Barlangi granophyre; Erickson et al, 2020), the 2023 ± 4 Ma Vredefort impact crater in South Africa (recrystallized pseudotachylitic breccia; Kamo et al, 1996), the 1850 ± 1 Ma Sudbury impact structure in Canada (impact melt sheet norite; Davis, 2008), the 608 ± 8 Ma Sääksjärvi impact structure in Finland (impact melt and impact melt breccias; Kenny et al, 2020), the 453 ± 3 Ma Brent impact structure in Canada (clast‐bearing impact melt rocks; McGregor et al, 2020), the approximately 385 Ma Nicholson Lake impact structure in Canada (impact melt‐bearing breccia and clast‐laden impact melt rock; McGregor et al, 2018), the approximately 252–255 Ma Araguainha impact structure in Brazil (impact melt in suevite; Hauser et al, 2019), the 215 ± 1 Ma Manicouagan impact structure in Canada (impact melt rock; Hodych & Dunning, 1992), the approximately 207 Ma Rochechouart impact structure in France (impact melt rock; Rasmussen et al, 2020), the 146.1 ± 0.2 Ma Morokweng impact structure in South Africa (impact melt sheet rocks; Hart et al, 1997; Kenny et al, 2021; Koeberl et al, 1997), the 123 ± 1 Ma Vargeão Dome in Brazil (melt vein in impact breccia; Nédélec et al, 2013—although it has been argued that this may not date the impact event itself; Crósta et al, 2019), the 78 ± 1 Ma Lappajärvi impact crater in Finland (impact melt rock; Kenny et al, 2019), the 37.8 ± 0.1 Ma Mistatin Lake impact crater in Canada (impact melt sheet; Sylvester et al, 2013), and the 14.9 ± 0.3 Ma Ries impact crater in Germany (impact melt rocks; Schwarz et al, 2020). In all these cases, dating was carried out on zircon from solidified impact melt and impact melt‐bearing lithologies.…”

Effect of Heterogeneity on the Diffusion of Pb in Apatite for Petrochronological Applications: A Multiscale Approach to Characterizing the Influence of Apatite Chemistry and Anisotropy on Pb Diffusion

“…A variety of minerals, including zircon, monazite, apatite, and iron oxides, have been employed for (U-Th)/Pb, He thermochronology in numerous geological applications (e.g., Barnes et al, 2021;Farley and Stockli, 2002;Schoene, 2014;Watson et al, 1985;Zeitler et al, 1987). Because of its high temperature sensitivity, the U -Pb method is well suited for studying tectonic stability, exhumation, the geologic history of tectonically active margins that may have been subjected to multiple terrane collisions, extra-terrestrial phenomena such as asteroid impact and ejection events, and rates of planetary accretion (Blackburn et al, 2011;Blackburn et al, 2012;McGregor et al, 2020). Strong quantitative understanding of the diffusion behaviour in geochronometric minerals is a prerequisite for a robust U-Th-Pb age interpretation as the closure temperature Tc (which denotes the temperature below which Pb are largely preserved during the process of cooling) of these minerals is a function of the diffusion behaviour (Dodson, 1973).…”

The response of zircon to the extreme pressures and temperatures of a lightning strike

“…Porous textures in zircon from impact melt rocks and impact melt-bearing breccias (e.g., refs. 18 , 19 ) have also been shown to accurately record impact ages. As such, it is important to understand if porosity in zircon is an inherited pre-impact feature of the grains or if it can form in impact environments (for example, in response to extreme pressures and temperatures or in response to post-impact hydrothermal alteration).…”