Paleomagnetic evidence for Neoarchean plate mobilism.

Plate tectonics is a unique feature of Earth, but its proposed time of initiation is still controversial, with published estimates ranging from ca. 4.2 to 0.7 Ga. Paleomagnetic data can provide a robust argument for one essential aspect of plate tectonics: large-scale relative lateral motions of distinct, rigid crustal blocks. Previously, the oldest relative horizontal motion between two or more blocks was constrained to a broad age interval of ca. 2.7-2.17 Ga using paleomagnetic data. In this study, we obtain a robust ca. 2.48 Ga paleomagnetic pole from Wyoming craton. Combining this result with the ca. 2.7-2.17 Ga apparent polar wander paths from Wyoming and Superior cratons, we suggest that they assembled during ca. 2.7-2.5 Ga and remained directly juxtaposed until ca. 2.17 Ga. Tectonostratigraphic data and geological proxies also suggest Wyoming and Superior collided at ca. 2.6 Ga. The results provide strong evidence for relative horizontal motion between crustal blocks during the Neoarchean. Together with other tectonic proxies, the data suggest plate mobilism in operation prior to 2.5 Ga.