The Role of Inherited Lithospheric Heterogeneities in Defining the Crustal Architecture of Rifted Margins and the Magmatic Budget During Continental Breakup

Abstract

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. In magma‐rich margins, the necking is accomplished by the emplacement of large amounts of volcanics in the continental‐ocean transition, in the form of seaward dipping wedges of flood basalts (seaward dipping reflections). 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 seaward dipping reflections 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.

Rifted Margins: State of the Art and Future Challenges

“…Most present-day rifted margins were built upon earlier continental collision zones. Progress has been made in defining different types of orogenic inheritance, including structural, thermal, and compositional inheritance (Manatschal et al, 2014;Gouiza and Paton, 2019). However, it remains difficult to characterize the different types of inheritance on the scale of rifted margins, and the way such inheritance is related to rift-induced processes such as, for instance, serpentinization and magmatism.…”

Conjugate margins — An oversimplification of the complex southern North Atlantic rift and spreading system?

“…Despite the research focus on the margins of the southern North Atlantic, the mechanisms driving extensional deformation in the continental domains leading to the creation of new oceanic crust, and thus passive margins, remains a topic of considerable current research interest (Nirrengarten et al, 2018;Gouiza and Paton, 2019). Current areas of research in this area include, but are not limited to: 1) timing of spatially and temporally overlapping and interacting rifting events (Gouiza et al, 2015), 2) sediment distribution, provenance and facies (Tyrrell et al, 2007), 3) timing of structural development and its relationship with hydrocarbon prospectivity (Enachescu et al, 2004), 4) the role of pre-existing structures in controlling rift evolution and margin architecture (Doré et al, 1999), and 5) the causes and consequences of rift-and breakup-related magmatism (Keen et al, 2014;Peace et al, 2018c).…”

Rheological inheritance controls the formation of segmented rifted margins in cratonic lithosphere

“…between the Labrador Sea and the Baffin Bay through the Davis Strait 4 ), or within a single basin (e.g. Labrador Sea 5 ). Thus, changes in rifting style, strain distribution, crustal architecture, timing, and nature of continental breakup can develop across distinct rifted margins and along the length of individual rift systems.…”