Igneous processes in impact melt sheets and controls on lithosphere evolution

The Earth experienced intensive impact bombardment from the Hadean to Palaeoarchaean, but the effects on lithosphere evolution are poorly understood. It has been hypothesized that bombardment led to near total reworking of the crust (Marchi et al, 2014), and may have resulted in differentiation of the lithosphere and the formation of early cratons (e.g. Grieve et al., 2006; Johnson et al., 2022). However, highly limited ancient rock records, and competing models for igneous processes operating in impact melt sheets, have precluded testing of these hypotheses and integration into models for Earth’s early evolution.

This project aims to test competing models for impact melt generation and melt sheet differentiation, capitalizing on two uniquely suited natural laboratories: the Sudbury impact structure, which contains Earth’s largest differentiated impact melt sheet and world-class Ni-Cu-PGE mineralisation, and the Kamestastin impact structure with a predominantly anorthositic target. The project will build on our advances in tracing superheated impact melt processes through microstructural phase heritage (White et al., 2020), and couple this with petrology, geochemistry, geochronology and thermodynamic modelling of melt evolution. Field study and sampling in both Canadian craters is planned, to complement existing sample sets. The outcomes will enhance understanding of Earth’s early evolution, ore-forming processes in Sudbury, and impact processes across the Solar system.