The Tristan da Cunha mantle plume, new insights from geophysical, petrological and geochemical studies along the Walvis Ridge hotspot track and at Tristan da Cunha Island

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• Wolfram Geissler, Alfred Wegener Institute
• Wednesday 28 February 2024, 16:00-17:00
• Wolfson Lecture Theatre.

If you have a question about this talk, please contact Megan Holdt.

Tristan da Cunha is a hotspot in the South Atlantic Ocean, located _{450 km east of the Mid-Atlantic Ridge. The intraplate volcanoes and seamounts that form the Tristan da Cunha archipelago are connected to the Cretaceous (}132 Ma) Etendeka continental flood basalt province in Namibia via the aseismic Walvis Ridge. The ridge is built-up by seamounts chains and submarine volcanic plateaus that show a clear age progression and extend from the Namibian continental margin (northeast) to the volcanic islands of Tristan da Cunha and Gough (southwest). This age-progressive distribution of volcanic rock samples collected from the Walvis Ridge and the Rio Grande Rise west of the Mid-Atlantic Ridge provide evidence for the volcanism at Tristan da Cunha and the formation of Cretaceous flood basalts in Namibia and Brazil to be due to a common hotspot source, with the Walvis Ridge and the Rio Grande Rise documenting the hotspot tracks. The Tristan da Cunha-Walvis Ridge system is one of the few examples of a complete hotspot track, and thus the it is generally assumed to be a surface expression of a long-lasting mantle plume. However, a debate continues about whether the mantle plume beneath Tristan da Cunha is an expression of convection of the whole mantle or of shallower plate-driven convection. NW Namibia, the Walvis Ridge, Tristan da Cunha, and the South Atlantic Ocean in general were target regions for various international geophysical and geochemical projects over the past two decades, including a recent IODP expedition to the Walvis Ridge. In my talk, I will summarize the recent findings with a special focus to the crust and upper mantle structure beneath the region around Tristan da Cunha.

This talk is part of the Bullard Laboratories Wednesday Seminars series.

This talk is included in these lists:

• Bullard Laboratories Wednesday Seminars
• Department of Earth Sciences seminars
• Wolfson Lecture Theatre

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