SURFACE HISTORY OF THE CRATONIC CANADIAN ARCTIC MARGIN REVEALED BY KIMBERLITE APATITE (U-TH)/HE DATING

How surface histories are linked with magmatism, lithospheric architecture, and large-scale tectonics are important questions in deciphering continental records. The Canadian Arctic provides an unusual opportunity to study these relationships. The region is characterized by lithosphere of varied thickness whose Phanerozoic evolution was affected by several episodes of rifting, major orogenic events, repeated kimberlite magmatism, and the Cretaceous High Arctic Large Igneous Province. Multiple large basins preserve a record of Phanerozoic sedimentation that once blanketed the Canadian Arctic, but the magnitude, timing, and spatial variability of burial and erosion across the northern margins of the Slave and Rae cratons and Arctic Archipelago is currently not well constrained.

Here we apply apatite (U-Th)/He (AHe) thermochronology to well-dated Phanerozoic igneous units, such as kimberlites, which place tighter constraints on Phanerozoic thermal histories than AHe analysis of Precambrian basement. Previous AHe analysis of basement apatite in the central-western Slave craton revealed several km of burial in the mid-Paleozoic, with a potential smaller episode of burial in the Cretaceous (Ault et al., 2013). New AHe results from three Eocambrian kimberlites from the Coronation Gulf suggest that a similar thermal history affected the northern Slave craton. Data for one mid-Cretaceous kimberlite from Somerset Island (Rae craton) are compatible with limited Cretaceous burial there, although unlike the Slave craton, this area still retains some of its Phanerozoic cover. On Victoria Island, where Phanerozoic cover is also still preserved, Permian kimberlites illuminate an unrecognized portion of this region’s thermal history, highlighting some degree of burial and erosion after emplacement. Our continuing work will refine the Phanerozoic surface history of the Slave and Rae cratons and extend the surface history to more tectonically complex areas in the Arctic Archipelago.