The role of inherited lithospheric heterogeneities in defining the crustal architecture of rifted margins and the magmatic budget during continental breakup

During the final stage of continental rifting, stretching localizes in the future distal domain where lithospheric necking occurs resulting in continental breakup. In magma-poor margins, the lithospheric necking is accompanied by crustal hyperextension, serpentinization and exhumation of mantle lithosphere in the continent-ocean transition domain (COT). In magma-rich margins, the necking is accomplished by the emplacement of large amounts of volcanics in the COT, in the form of seaward dipping wedges of flood basalts (SDRs). This study examines the factors controlling the final crustal architecture observed in rifted margins and the magmatic budget during continental breakup, using observations from the Labrador Sea. The latter shows magma-rich breakup with SDRs documented in the north and magma-poor breakup with a wide domain of exhumed serpentinized mantle recorded in the south. The pre-rift strength of the lithosphere, defined by the inherited thermal structure, composition, and thickness of the lithospheric layers, controls the structural evolution during rifting. While variations in the magmatic budget associated with breakup are controlled primarily by the interaction between the pre-rift inheritance, the timing and the degree of mantle melting, in relation to lithospheric thinning and mantle hydration.