Multistage exhumation and juxtaposition of lower continental crust in the western Canadian Shield: Linking high-resolution U-Pb and40Ar/39Ar thermochronometry with pressure-temperature-deformation paths

摘要: [1] New U-Pb (titanite, apatite, rutile) and 40Ar/39Ar (hornblende, muscovite, biotite) data are linked with existing pressure-temperature-deformation paths to impose detailed temporal constraints on the juxtaposition unroofing of domains in an extensive (>20,000 km2) region exhumed lower crust East Lake Athabasca western Canadian Shield. In ∼200 m.y. between circa 1.9 Ga high-pressure granulite facies metamorphism 1.7 unconformable deposition basin sediments rocks, our analysis reveals at least three distinct phases different rates. Specifically, we distinguish (1) early phase extensional Chipman domain rates 1.5–2.0 km/m.y. from ∼1.0 GPa ∼0.8 associated mafic magmatism metamorphism, (2) episode regional contractional uplift along Legs shear zone 1850 Ma 0.7–0.8 0.4–0.5 GPa, (3) a final period 0.2–0.3 0.4 0.5 that culminated transport current exposures near-surface conditions. The cooling patterns retrograde assemblages consistent pauses exhumational phases. apparent convergence disparate higher temperature histories several deep crustal 1.89–1.88 implies their Regional east directed thrusting as coherent unit 1.85 juxtaposed granulites middle Hearne rocks history allows correlation changing tectonic regimes amalgamation Laurentia. spatial heterogeneity exhumation may be common feature rocks.