Breakup of strong cratonic lithosphere causes extensive magmatism at continental margins

Extensive magmatism and Large Igneous Provinces (LIPs) may form at continental margins during continental breakup. While high mantle temperatures and geochemical fertility (such as plume activity) are typically considered the causes of magmatic generation, the role of lithospheric strength remains underexplored. Here, we employ two-dimensional thermomechanical models to reveal that rifting within strong cratonic lithosphere can trigger a pronounced syn-breakup magmatic surge, which may be responsible for the formation of volcanic margins and even LIPs characterized by syn-breakup magmatism. This surge results from enhanced asthenospheric upwelling driven by the collapse of elevated rift flanks, a process that occurs only when lithospheric strength is sufficiently high. Multidisciplinary evidence from the Labrador Sea-Baffin Bay rift system supports this mechanism, linking its excessive magmatism to high lithospheric strength. This framework demonstrates that such excessive magmatism does not require an anomalously hot mantle or special mantle fertility, offering a new perspective on the genesis of volcanism and LIPs along continental margins.