Evidence for a 1.24-1.21 Ga large igneous province in the North China Craton

Mafic dyke swarms represent the plumbing system of large igneous provinces, which is often associated with mantle plumes and supercontinent cycles. Geochronological, geochemical, and paleomagnetic studies of such dyke swarms provide unique constraints on paleogeographic reconstructions. Mafic dyke swarms that intrude the North China Craton (NCC) are still poorly explored. New ca. 1.24 Ga and ca. 1.21 Ga mafic dykes have recently been identified in eastern NCC through baddeleyite dating. Geochemical results both from the literature and obtained during this study reveal an alkaline basalt composition and an intraplate tectonic setting for these dykes with OIB-like characteristics (e.g., La/Yb values of 13 and low Zr/Nb ratio of 6-13). In addition to plume-related geochemical signatures, the radiating geometry of the dykes is also a clear indication of a 1.24-1.21 Ga large igneous province due to a mantle plume event, probably related to the break-up of the supercontinent Nuna. The geometry of the dykes and their magnetic fabric suggest a magmatic centre in present-day southeastern NCC. We obtain a 1.24 Ga paleomagnetic pole and a 1.21 Ga VGP from these dykes, with the 1.24 Ga pole passing a baked contact test. These new paleopoles constrain the independent motion of the North China Craton after the breakup of Nuna.