TRISTAN: Electromagnetic, gravimetric and seismic measurements to investigate the Tristan da Cunha hot spot and its role in the opening of the South-Atlantic - Cruise No. MSM20/2 - January 17 - February 15, 2012 - Walvis Bay (Namibia) - Recife (Brazil) (English)

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According to classical plume theory, the Tristan da Cunha hotspot is thought to have played a major role in the rifting of the South Atlantic margins and the creation of the aseismic Walvis Ridge by impinging at the base of the continental lithosphere shortly before or during the breakup of the South Atlantic margins. But Tristan da Cunha is enigmatic, as it cannot be clearly identified as a hot-spot but classifies also highly as a more shallow type of anomaly that may actually have been caused by the opening of the South Atlantic. The equivocal character of Tristan is largely due to lack of geophysical data in this region. To understand the tectonic processes of the opening of the South Atlantic, the formation of the Walvis ridge and to understand whether Tristan da Cunha is the cause or the consequence of rifting, it is of central importance to characterize the region around Tristan da Cunha in a more coherent way. Within this research cruise we deployed 26 ocean bottom electromagnetic stations (OEBM) and 24 ocean bottom seismometer (OBS) for a long term acquisition (1 year) of magnetotelluric and seismological data, acquired bathymetry and gravity data and performed geological sampling on Tristan da Cunha. The data will be interpreted in the context of geochemical data and tectonic models developed within the SPP1375 South Atlantic Margin Processes and Links with onshore Evolution (SAMPLE).