Numerical Modeling of Purely Active (Plume-Produced) Continental Rifting and Break-Up

Abstract

In contrast to the traditional mechanism of passive continental rifting (driven by far-field tectonic forces), the active rifting-to-break-up processes (caused by rising mantle plumes) are still poorly understood. However, most episodes of fragmentation of the last supercontinent Pangea were relatively shortly preceded (within ∼10 Myr) by the emplacement of Large Igneous Provinces, indicating that a link between lithospheric ruptures and mantle plumes is very close and frequent. In this study, we present a systematic numerical modeling of purely active continental rifting and break-up, that is, without far-field extension, examining the following parameters: (a) the thermo-rheological structure of the lithosphere, (b) the buoyancy of the thermo-chemical mantle plume anomaly, and (c) the duration of the incoming plume flux. Thermo-mechanical experiments show that a classic active rifting scenario, involving the complete break-up of the lithosphere within less than 10 Myr following the arrival of a mantle plume, is achievable, though only under specific conditions. These include: (a) a continuously fed plume with an elevated thermal and/or compositional density deficit ((Formula presented.) ≤ −30 kg m−3) and (b) a relatively warm overlying continental plate, characterized by an above-average Moho temperature ((Formula presented.) = 750°C). Although both prerequisites do not seem entirely unrealistic, their simultaneous occurrence in the Phanerozoic Earth is unlikely. We therefore conclude that for a successful transition to lithospheric break-up, plume-activated continental rifting events in the Mesozoic–Cenozoic time must be accompanied by external tectonic stresses.