70 Ma Chemical Zonation of the Tristan-Gough Hotspot Track


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Wilfried.Jokat [ at ] awi.de

Abstract

Asymmetrically zoned hotspot tracks in the Pacifi c Ocean are interpreted to have formed from zoned plumes originating from the large-scale, lower-mantle, low-seismic-velocity anomaly (superplume?) beneath the southern Pacifi c, providing direct information about lowermantle compositional heterogeneity. New trace-element and Sr-Nd-Hf-Pb isotope data from the classic Tristan-Gough hotspot track in the South Atlantic also display a bilateral, asymmetric zonation with two distinct mantle source components, making it the fi rst zoned plume to be recognized overlying the African superplume. The plume zonation can be traced for 70 m.y., four times longer than recognized for Pacifi c zoned hotspot tracks. These fi ndings confi rm that the proposed zonation of Pacifi c hotspots is not simply a geochemical oddity, but could be a major feature of plumes derived from lower-mantle superplumes. We propose that the enriched southern Gough subtrack source with elevated 207Pb/204Pb and 208Pb/204Pb at a given 206Pb/204Pb, but low 143Nd/144Nd and 176Hf/177Hf (DUPAL-like composition), may refl ect the African superplume composition, whereas the more depleted northern Tristan subtrack source could represent a mixture of the superplume with the surrounding depleted mantle. Our results strengthen arguments that the enriched signature (DUPAL anomaly) in the South Atlantic could be derived from the lower mantle.



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Article
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ISI/Scopus peer-reviewed
Publication Status
Published
Eprint ID
31285
DOI 10.1130/G33790.1

Cite as
Rohde, J. , Hoernle, K. , Hauff, F. , Werner, R. , O'Connor, J. , Class, C. , Garbe-Schönberg, D. and Jokat, W. (2013): 70 Ma Chemical Zonation of the Tristan-Gough Hotspot Track , Geology, 41 (3), pp. 335-338 . doi: 10.1130/G33790.1


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