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SUMMARY:The Tristan da Cunha mantle plume\, new insights from geophysical\
 , petrological and geochemical studies along the Walvis Ridge hotspot trac
 k and at Tristan da Cunha Island - Wolfram Geissler\, Alfred Wegener Insti
 tute
DTSTART:20240228T160000Z
DTEND:20240228T170000Z
UID:TALK210994@talks.cam.ac.uk
CONTACT:Megan Holdt
DESCRIPTION:Tristan da Cunha is a hotspot in the South Atlantic Ocean\, lo
 cated ~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 Namibi
 a via the aseismic Walvis Ridge. The ridge is built-up by seamounts chains
  and submarine volcanic plateaus that show a clear age progression and ext
 end from the Namibian continental margin (northeast) to the volcanic islan
 ds of Tristan da Cunha and Gough (southwest). This age-progressive distrib
 ution of volcanic rock samples collected from the Walvis Ridge and the Rio
  Grande Rise west of the Mid-Atlantic Ridge provide evidence for the volca
 nism 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.\nThe Tristan
  da Cunha-Walvis Ridge system is one of the few examples of a complete hot
 spot track\, and thus the it is generally assumed to be a surface expressi
 on of a long-lasting mantle plume. However\, a debate continues about whet
 her the mantle plume beneath Tristan da Cunha is an expression of convecti
 on of the whole mantle or of shallower plate-driven convection.\nNW Namibi
 a\, the Walvis Ridge\, Tristan da Cunha\, and the South Atlantic Ocean in 
 general were target regions for various international geophysical and geoc
 hemical projects over the past two decades\, including a recent IODP exped
 ition to the Walvis Ridge. In my talk\, I will summarize the recent findin
 gs with a special focus to the crust and upper mantle structure beneath th
 e region around Tristan da Cunha.
LOCATION:Wolfson Lecture Theatre
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