Zircon formation in impact melts: Complications for deciphering planetary impact histories

Zircon grains in impact melts may not reliably record planetary impact events, challenging their use as geochronological markers. Modeling suggests zircon formation is rare (~2% of melting events) and requires high zircon abundance, making it unlikely for lunar meteorites like SaU 169 to reflect Imbrium impact ages. Analysis of poikilitic zircons from the Vredefort Dome, Earth's largest terrestrial impact crater, reveals they are inherited from Archean target rocks with Pb loss, not formed during the impact. This complicates the interpretation of zircon textures in lunar samples and underscores the need for further study on shock-induced isotopic effects to accurately decipher planetary impact histories.

Wielicki, M. M., & Harrison, T. M. Zircon formation in impact melts: Complications for deciphering planetary impact histories. Large Meteorite Impacts and Planetary Evolution V, 127–134. https://doi.org/10.1130/2015.2518(08)