The Manicouagan impact melt sheet: Evidence for isotopic homogenization with limited assimilation

The Rb–Sr, Pb–Pb and Sm–Nd isotope chemistry of impact-generated melt and target rocks has been determined from the 214Ma, ∼90km rim-diameter, Manicouagan impact structure of Canada. Fifty-seven samples were obtained from 8 field sites and 11 drill core sites across the impact melt sheet, located on the 55km-diameter central island (Île René-Levasseur). The results reveal that the impact melt, though locally differentiated via fractional …