Exploring Relationships between Kimberlite Distributions, Mantle Dynamics, and the Hypsometric History of the North American Cratonic Interior

English Abstract:

Numerous explanations have been put forth for the apparently episodic emplacement of kimberlites in cratons. It is increasingly recognized that many cratons underwent vertical motions in the Phanerozoic, but how cratonic elevation change histories relate to the kimberlite record has received relatively little attention. Our recent work suggests causal links between kimberlite distributions, mantle flow associated with supercontinent evolution, and cratonic surface histories. By coupling apatite (U-Th)/He thermochronometry with diverse geologic constraints, we have resolved substantial Phanerozoic burial (1-4 km), unroofing, and elevation change episodes across the Slave craton and begun characterizing the spatial heterogeneity of missing pieces of the Phanerozoic sedimentary record more broadly across the Canadian shield. The long-wavelength (>1000 km) character of the vertical motions and their occurrence far from plate boundaries points toward dynamic topography as the cause. The Slave craton elevation change history is similar to the vertical motions predicted by a 3D model of thermochemical convection during Pangea evolution, implying that mantle flow associated with supercontinent assembly and breakup influenced the hypsometric history of the North American cratonic interior. We also find a broad synchroneity between gaps in emplacement times of Slave and Superior craton kimberlites and regional burial phases. This pattern suggests: 1) a common mantle dynamic control on kimberlite magmatism and cratonic vertical motions during supercontinent evolution, and/or 2) that some gaps in the kimberlite record are preservational artifacts because the uppermost portions of kimberlites emplaced during burial phases would have been largely removed during subsequent erosion along with the strata into which they were emplaced. Together these relationships imply that cratonic surface histories and their causes are important for understanding global kimberlite distributions.