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. (doi: 10.1002/2014GC005648)

Abstract

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: Articles
• Additional Information: Funding was provided by NERC grants NE/E007414/1, NE/ D008611/1, and NE/J012297/1, NSF grant EAR-0635789, and BHP-Billiton. J.O.S.H. was supported by NERC Fellowship NE/I020342/1
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Thompson, Dr David
• Authors: Thompson, D.A., Hammond, J. O. S., Kendall, J.-M., Stuart, G. W., Helffrich, G. R., Keir, D., Ayele, A., and Goitom, B.
• College/School: University Services > Research Strategy and Innovation > Research and Innovation Services
• Journal Name: Geochemistry, Geophysics, Geosystems
• Publisher: American Geophysical Union
• ISSN: 1525-2027
• ISSN (Online): 1525-2027
• Copyright Holders: Copyright © 2015 The Author(s)
• First Published: First published in Geochemistry, Geophysics, Geosystems 16(3):834-846
• Publisher Policy: Reproduced under a creative commons licence