In Situ Lu–Hf Garnet Dating of Archean Deep Crust Granulites from the Polymetamorphic Grenville Front Tectonic Zone.

This article focuses on applying in situ lutetium-hafnium (Lu–Hf) garnet geochronology combined with trace element mapping to constrain the timing and extent of polymetamorphic events in the Grenville Front Tectonic Zone (GFTZ) of the southeastern Superior Craton, Canada. The study reveals that granulite-facies metamorphism in parautochthonous Archean rocks predominantly dates to the late Neoarchean (~2.6 billion years ago), with only limited local disturbance of the Lu–Hf system attributed to fluid-assisted alteration during the Mesoproterozoic Grenvillian Orogeny (~1 billion years ago). These findings suggest that the GFTZ exposes rare Archean lower crust with minimal Grenvillian overprint, providing insights into the tectono-thermal evolution and cratonization processes of the region. The research demonstrates the effectiveness of in situ Lu–Hf garnet dating in resolving complex metamorphic histories in polymetamorphic terranes.