Comment on ‘The challenge in restoring magma-rich rifted margins: The example of the Mozambique-Antarctica conjugate margins’ by Tomasi S. et al

AbstractTo accurately reconstruct plate configurations, there is a need for a quantitative method to calculate the amount and timing of crustal extension independent of any one model for the formation of rifted margins. This paper evaluates the suitability of the various plate modelling methods for structural inheritance studies and proposes a classification scheme for the methods that are currently in use. A palinspastic deformable margin plate kinematic model is most suitable for tectonic inheritance studies, particularly at hyperextended margins. This type of plate model provides a valuable analytical tool that can be used to show the temporal and spatial relationship between pre-existing orogenic structures, evolving rift axes and global plate reorganization events. We use a palinspastic deformable margin plate model for the southern North Atlantic and Labrador Sea to quantitatively restore up to 350 km of Mesozoic–Cenozoic extension. This provides us with a pre-rift restoration of the Proterozoic and Paleozoic terranes and structural lineaments on the conjugate margins that helps us to analyse their relationship to evolving rift axes and global plate reorganization events through time. Interpretation of these modelling results has led to a clearer understanding of the relationship between inherited structural features and their control on rifting and the break-up history.

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Melt volume at Atlantic volcanic rifted margins controlled by depth-dependent extension and mantle temperature

Nature Communications ◽

10.1038/s41467-021-23981-5 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Gang Lu ◽

Ritske S. Huismans

Keyword(s):

Numerical Models ◽

Potential Temperature ◽

Analytical Prediction ◽

Natural Systems ◽

Passive Margins ◽

Margin Width ◽

Rifted Margins ◽

Mantle Potential Temperature ◽

Mantle Temperature ◽

Rifted Margin

AbstractBreakup volcanism along rifted passive margins is highly variable in time and space. The factors controlling magmatic activity during continental rifting and breakup are not resolved and controversial. Here we use numerical models to investigate melt generation at rifted margins with contrasting rifting styles corresponding to those observed in natural systems. Our results demonstrate a surprising correlation of enhanced magmatism with margin width. This relationship is explained by depth-dependent extension, during which the lithospheric mantle ruptures earlier than the crust, and is confirmed by a semi-analytical prediction of melt volume over margin width. The results presented here show that the effect of increased mantle temperature at wide volcanic margins is likely over-estimated, and demonstrate that the large volumes of magmatism at volcanic rifted margin can be explained by depth-dependent extension and very moderate excess mantle potential temperature in the order of 50–80 °C, significantly smaller than previously suggested.

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Crustal variability along the rifted/sheared East African margin: a review

Geo-Marine Letters ◽

10.1007/s00367-021-00690-y ◽

2021 ◽

Vol 41 (2) ◽

Author(s):

Maren Vormann ◽

Wilfried Jokat

Keyword(s):

East Africa ◽

Shear Zone ◽

Structural Changes ◽

The South ◽

East African ◽

The North ◽

Rifted Margins ◽

Continental Block ◽

Seismic Lines ◽

Southeastern Madagascar

AbstractThe East African margin between the Somali Basin in the north and the Natal Basin in the south formed as a result of the Jurassic/Cretaceous dispersal of Gondwana. While the initial movements between East and West Gondwana left (oblique) rifted margins behind, the subsequent southward drift of East Gondwana from 157 Ma onwards created a major shear zone, the Davie Fracture Zone (DFZ), along East Africa. To document the structural variability of the DFZ, several deep seismic lines were acquired off northern Mozambique. The profiles clearly indicate the structural changes along the shear zone from an elevated continental block in the south (14°–20°S) to non-elevated basement covered by up to 6-km-thick sediments in the north (9°–13°S). Here, we compile the geological/geophysical knowledge of five profiles along East Africa and interpret them in the context of one of the latest kinematic reconstructions. A pre-rift position of the detached continental sliver of the Davie Ridge between Tanzania/Kenya and southeastern Madagascar fits to this kinematic reconstruction without general changes of the rotation poles.

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