Imperial College London
Alternate

Dr Ian Bastow

Faculty of Engineering, Department of Earth Science & Engineering

Senior Lecturer
 
 
 
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Contact

 

+44 (0)20 7594 2974i.bastow Website

 
 
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Location

 

4.45Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Pugh:2023:10.1029/2022GC010782,
author = {Pugh, S and Boyce, A and Bastow, I and Ebinger, C and Cottaar, S},
doi = {10.1029/2022GC010782},
journal = {G3: Geochemistry, Geophysics, Geosystems: an electronic journal of the earth sciences},
pages = {1--22},
title = {Multigenetic origin of the X-discontinuity below continents: insights from African receiver functions},
url = {http://dx.doi.org/10.1029/2022GC010782},
volume = {24},
year = {2023}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - Constraints on chemical heterogeneities in the upper mantle may be derived from studying the seismically observable impedance contrasts that they produce. Away from subduction zones, several causal mechanisms are possible to explain the intermittently observed X-discontinuity (X) at 230–350 km depth: the coesite-stishovite phase transition, the enstatite to clinoenstatite phase transition, and/or carbonated silicate melting, all requiring a local enrichment of basalt. Africa hosts a broad range of terranes, from Precambrian cores to Cenozoic hotspots with or without lowermost mantle origins. With the absence of subduction below the margins of the African plate for >0.5 Ga, Africa presents an ideal study locale to explore the origins of the X. Traditional receiver function (RF) approaches used to map seismic discontinuities, such as common conversion-point stacking, ignore slowness information crucial for discriminating converted upper mantle phases from surface multiples. By manually assessing depth and slowness stacks for 1° radius overlapping bins, normalized vote mapping of RF stacks is used to robustly assess the spatial distribution of converted upper mantle phases. The X is mapped beneath Africa at 233–340 km depth, revealing patches of heterogeneity proximal to mantle upwellings in Afar, Canaries, Cape Verde, East Africa, Hoggar, and Réunion with further observations beneath Cameroon, Madagascar, and Morocco. There is a lack of an X beneath southern Africa and strikingly, the magmatic eastern rift branch of the southern East African Rift. With no relationships existing between depth and amplitudes of observed X and estimated mantle temperatures, multiple causal mechanisms are required across a range of continental geodynamic settings.
AU  - Pugh,S
AU  - Boyce,A
AU  - Bastow,I
AU  - Ebinger,C
AU  - Cottaar,S
DO  - 10.1029/2022GC010782
EP  - 22
PY  - 2023///
SN  - 1525-2027
SP  - 1
TI  - Multigenetic origin of the X-discontinuity below continents: insights from African receiver functions
T2  - G3: Geochemistry, Geophysics, Geosystems: an electronic journal of the earth sciences
UR  - http://dx.doi.org/10.1029/2022GC010782
UR  - https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022GC010782
UR  - http://hdl.handle.net/10044/1/103406
VL  - 24
ER  -
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