Precambrian plate tectonics: Seismic evidence from northern Hudson Bay, Canada

Abstract

The Canadian Shield is one of the largest exposures of Precambrian rocks on Earth. It is a mosaic of several Archean terranes that were brought together during a series of Paleoproterozoic orogens culminating in the so-called Trans-Hudson orogen, which is thought to have been similar to the Himalayan orogen in scale and nature. The tectonic evolution and lithospheric subdivisions of this region are poorly understood, but new seismic networks in northern Hudson Bay provide fresh opportunity to place constraints on the Precambrian processes that formed and shaped it. We show, via a study of seismic anisotropy, that the lithosphere of the northern Hudson Bay region retains a strong signature of Archean-Paleoproterozoic tectonics. We map the boundary between the upper (Churchill) and lower (Superior) plates that collided ca. 1.8 Ga and identify back azimuthdependent splitting parameters (φ, δt) on Baffi n Island that indicate complex anisotropy (e.g., dipping fabric) beneath the region. Our results support the view that signifi cant lithospheric deformation occurred during the Paleoproterozoic and that modern-day plate tectonic processes were thus in operation by at least ca.

Upper mantle anisotropy of the Borborema Province, NE Brazil: Implications for intra-plate deformation and sub-cratonic asthenospheric flow

“…The region apparently affected by the Trans-Hudson Orogen is also extremely broad (≥ 250 km wide). These observations, coupled with splitting delay times of δt ≥ 1 s, were interpreted by Bastow et al (2011) as evidence that the Trans Hudson Orogen was Himalayan in scale (e.g., St-Onge et al, 2006). Splitting delay times at many stations in the Borborema Province are markedly lower than in northern Canada: only null observations are found at stations NBTA and NBMA, while δt is relatively low at NBLI and PFBR.…”

“…Such tectonic deformation, developed during the collisions of the Brasiliano/Pan-African orogeny, would be expected to have imprinted a strong anisotropic fabric on the lithospheric mantle. For example, plate-scale terrane boundaries that delineate the Paleoproterozoic Trans-Hudson Orogen in northern Canada are characterised by strong seismic anisotropic fossil fabrics, with fast polarisation directions that parallel the strike of the suture between two Archean continental blocks (Bastow et al, 2011). The region apparently affected by the Trans-Hudson Orogen is also extremely broad (≥ 250 km wide).…”

Large variations in lithospheric thickness of western Laurentia: Tectonic inheritance or collisional reworking?

“…This model implies a lack of pervasive deformation of the lower lithosphere during or after accretion. Coherent lithospheric fabrics that formed during the Archean and survived subsequent Proterozoic tectonic events have also been documented in other cratons, such as the Canadian Shield (Bastow et al, 2011;Kay et al, 1999;Snyder et al, 2013) and the Kaapvaal craton of South Africa (Silver et al, 2001).…”

CAN‐HK: An a Priori Crustal Model for the Canadian Shield

“…Data from temporary deployments associated with the Hudson Bay Lithospheric Experiment (HuBLE) (e.g., Thompson et al, 2010Thompson et al, , 2011Pawlak et al, 2011;Steffen et al, 2012;Bastow et al, 2015) are also used. In total, 134 broadband seismic stations contribute to the CAN-HK crustal model, providing unparalleled coverage and resolution for the Canadian shield (Fig.…”

“…The new model presented here, CAN-HK, utilizes new passive broadband deployments in the region (Eaton et al, 2005;Bastow et al, 2015). For several key tectonic features of the Canadian shield ( Fig.…”