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John O'Connor, VU University Amsterdam (Netherlands)
Peter Stoffers, Christian-Albrechts-University (Germany)
Jan Wijbrans, VU University Amsterdam (Netherlands)
Wilfried Jokat, Alfred Wegener Institute for Polar and Marine Research (Germany)
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When quantifying plate motions and their uncertainties relative to hotspots it is widely assumed that the locations and dimensions of volcanically active 'hotspots' are broadly similar to those of their underlying mantle sources. We are showing, however, on the basis of new sampling and dating of Pacific seamounts and volcanic ridges, that hotspot mantle influences a broader region under the lithosphere than is reflected by hotspot trails. For example, in the case of the Galapagos Volcanic Province we show a progression of broad regions of long-lived and possibly concurrent volcanism that we link to a correspondingly broad hotspot melting anomaly (O'Connor et al., 2007). Similarly, our direct age dating of the Foundation Seamount Chain, SE Pacific, suggests that the narrowness of seamount chains might mask significantly broader regions of hotspot mantle (O'Connor et al., 2002, 2004). Improving our knowledge of the hotspot volcanic record with a view to understanding the interaction between hotspot mantle and tectonic plates is necessary in order to locate any underlying fixed mantle sources, whether moving or stationary. While this is being attempted at a number of different hotspots it also seems advisable to develop new strategies to resolve the relative contributions of plate and mantle motions to propagation rates of volcanism along hotspot trails. One notion is to cast a wider net by sampling multiple seamount chains and ridges scattered across a broad region of lithosphere in an effort to pin down one or more fixed or moving mantle sources supplying hotspot mantle responsible for scattered widespread volcanism. We have therefore embarked on such a quest in the S. Atlantic by initially focusing on sampling hotspot seamounts and ridges to the south of Walvis Ridge using the robust R/V Polarstern.
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