Dating shear zones with plastically deformed titanite: New insights into the orogenic evolution of the Sudbury impact structure (Ontario, Canada)

•Age dating of mylonitic shearing with dynamically recrystallized titanite grains.•Ductile shear zones in the South Range of the Sudbury structure operated during the Mazatzalian-Labradorian orogeny (1.7-1.6 Ga).•Shear-hosted sulphides in Creighton Mine exhibit mechanical remobilization structures.•The CPO in titanite grains is not reset by dissolution-precipitation deformation mechanisms in epidote-amphibolite facies conditions.

The Sudbury structure is a mineralized impact crater that hosts different families of ore-controlling shear zones with poorly known orogenic affinities. Discriminating whether these deformation events relate to the 1.85 Ga crater modification stage or later regional tectonism, that collapsed the impact structure, is important both for crustal and mineral exploration studies. We have combined underground mapping with isotopic and microstructural analysis of titanite and host minerals in a benchmark ore-controlling mylonitic shear zone of the mining camp, the Six Shaft Shear Zone from the Creighton Mine. Three growth stages of chemically and microstructurally-characterised titanite grains were identified related with the pre-, syn and late deformation stages. In-situ U-Pb age dating of the syndeformational grains demonstrates that a shearing event took place at 1645 ± 54 Ma during the Mazatzalian-Labradorian orogeny (1.7-1.6 Ga). This event led to the plastic deformation and local-scale remobilization of primary Ni-Cu-PGE sulphides in Creighton Mine (Sudbury, South Range). The adopted novel petrochronological approach can reveal the age significance of syn-deformational processes and holds promise for the untangling of complex syn-orogenic processes in Precambrian terranes globally.