Magma-assisted fragmentation of a supercontinent

Continental breakup often occurs within LIPs, and syn-rift sedimentary basins generally precede the main pulse of volcanism. However, the cause-and-effect relationship between pre-magmatic rifting and the extrusion of large amount of magma is controversial. Many studies have investigated the breakup processes of the continental lithosphere, among which the passive and active mantle models are considered end-member situations that precede continental fragmentation. However, it remains unclear whether magmatism arises as a consequence of passive rifting or whether it is related to active upwelling of the mantle. In addition, the relationship between the pre-magmatic stages and the final breakup, with the onset of conjugate passive margins, is ambiguous. In this study, we compiled available data from six LIPs (Central Atlantic, Karoo, Parana-Etendeka, Deccan, North Atlantic, and Afar igneous provinces) in the context of the Pangea fragmentation to (1) examine the spatiotemporal relationship between pre-magmatic continental extension and the onset of regional magmatism; (2) characterize the continental breakup propagation from the nuclei where breakup originates, and (3) discuss the role of mantle melting during supercontinental disintegration and propose a general evolution model that describes supercontinental fragmentation processes. We conclude that syn-magmatic rifts should not be directly correlated, both structurally and dynamically, to the ancient pre-magmatic rift phase. Furthermore, following the breakup of a supercontinent, seafloor spreading usually initiates within volcanic passive margins (VPMs) and then propagates away to create non-volcanic passive margins (NVPMs) as a consequence of the consumption and cooling of a sub-lithospheric positive thermal anomaly. Major transform faults often exist between VPMs and NVPMs, acting as a mechanical barrier.