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Hydrous upwelling across the mantle transition zone beneath the Afar Triple Junction

Thompson, D. A., Hammond, J. O. S., Kendall, J.-M., Stuart, G. W., Helffrich, G. R., Keir, D., Ayele, A. and Goitom, B. 2015. Hydrous upwelling across the mantle transition zone beneath the Afar Triple Junction. Geochemistry, Geophysics, Geosystems 16 (3) , pp. 834-846. 10.1002/2014GC005648

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The mechanisms that drive the upwelling of chemical heterogeneity from the lower to upper mantle (e.g., thermal versus compositional buoyancy) are key to our understanding of whole mantle convective processes. We address these issues through a receiver function study on new seismic data from recent deployments located on the Afar Triple Junction, a location associated with deep mantle upwelling. The detailed images of upper mantle and mantle transition zone structure illuminate features that give insights into the nature of upwelling from the deep Earth. A seismic low-velocity layer directly above the mantle transition zone, interpreted as a stable melt layer, along with a prominent 520 km discontinuity suggest the presence of a hydrous upwelling. A relatively uniform transition zone thickness across the region suggests a weak thermal anomaly (<100 K) may be present and that upwelling must be at least partly driven by compositional buoyancy. The results suggest that the lower mantle is a source of volatile rich, chemically distinct upwellings that influence the structure of the upper mantle, and potentially the chemistry of surface lavas.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: Q Science > QE Geology
Uncontrolled Keywords: Mantle; Body waves; Tomography; Hotspots, large igneous provinces, and flood basalt volcanism; Africa
Additional Information: This is an open access article under the terms of the Creative Commons Attribution License
Publisher: American Geophysical Union (AGU)
ISSN: 1525-2027
Date of First Compliant Deposit: 25 September 2020
Date of Acceptance: 20 February 2015
Last Modified: 25 Sep 2020 12:45

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