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Geophysical image of the continent-ocean boundary, implications on mantle dynamics and lithospheric controls on continental breakup in the South Atlantic

Principal Investigators: Dr. Soenke Neben, Dr. Bernd Schreckenberger, Dr. Dieter Franke

The South Atlantic, south of the Rio Grande Rise/Walvis Ridge, is a key study area to investigate the early evolution of continental breakup with special focus on a volcanic rifted margin environment. We want to investigate two conjugate margin segments with regard to the crustal architecture and furthermore to model the thermal structure of the mantle along the margin. BGR acquired unique marine geophysical data sets (> 30,000 line km) along the conjugate volcanic passive margins of the South Atlantic. First investigations on single aspects of the data sets and the preliminary results of the most recent field surveys showed that the South Atlantic margins are of the volcanic type over most of their length. The intensity and timing of volcanism was highly variable along the margins, ranging from thick igneous plateaus (Rio Grande Rise/Walvis Ridge) and flood basalt provinces (Parana/Etendeka) at the former location of the Tristan da Cunha hotspot during breakup, to obviously minor magmatic activity at the southernmost segments of the conjugate margins. Within the proposed study we will investigate in detail the deep structure of the South African margin that is the conjugate margin segment of the well studied Argentine margin. The study will resolve the variability of structures along the margins and will evaluate possible symmetries/asymmetries between conjugated margin segments. The results will be used to estimate the amount of emplaced volcanic material. These results will then be further input into thermal modeling to decipher the syn- and postrift development of the conjugated margin segments with focus on the magmatic processes. We expect that this enables us to discriminate between different rift models and mechanisms for the generation/emplacement of syn-rift volcanic rocks and their spatial/temporal variability.