THERMAL RECORDS OF LOWER CRUSTAL XENOLITHS AND GRANULITE EXPOSURES: A PERSPECTIVE FROM GRANULITES OF THE SNOWBIRD TECTONIC ZONE, NORTHERN SASKATCHEWAN
New U-Pb thermochronologic data place precise constraints on the timing of high-grade metamorphic events and subsequent exhumation of granulites in the East Athabasca area. Two episodes of high-grade metamorphism recorded in mafic granulites at ca. 2.54 Ga and ca. 1.9 Ga imply deep crustal residence within a stable lithosphere for ca. 640 m.y. Lithospheric reactivation at ca. 1.9 Ga is recorded by 1896 Ma amphibolite anatexis (> 750 °C) of a major mafic dike swarm intruded into one of the domains. Subsequent cooling to < 450 °C by ca. 1.76 Ga is recorded by titanite, apatite and rutile. Contrasts in cooling records between domains may indicate variability in isobaric cooling and exhumation. This perspective on deep crustal thermal evolution from the unique East Athabasca exposure can shed insight into the xenolith record and provide a better understanding of lithospheric growth, stabilization, and reactivation.