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{Chiasera:2021:10.1016/j.lithos.2021.106494,
author = {Chiasera, B and Rooney, T and Bastow, I and Yirgu, G and Grosfils, E and Ayalew, D and Mohr, P and Zimbelman, J and Ramsey, M},
doi = {10.1016/j.lithos.2021.106494},
journal = {Lithos},
pages = {1--16},
title = {Magmatic rifting in the Main Ethiopian Rift began in thick continental lithosphere; the case of the Galema range},
url = {http://dx.doi.org/10.1016/j.lithos.2021.106494},
volume = {406-407},
year = {2021}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - The northern Main Ethiopian Rift (MER) in East Africa is considered a region of incipient oceanic spreading, with Miocene border faulting now largely abandoned at the expense of magmatic extension in the Wonji Fault Belt (WFB). However, whether magmatic extension began when the Ethiopian lithosphere was still-thick, or heavily stretched, is unknown. TheGalema range, a linear Pliocene dike swarm parallel to the eastern margin of the present-day central MER, is an ideal study locale to constrain melting depths, and by inference the thickness of the lithosphere, during early magmatic rifting. To address this issue, we present whole-rock, trace element data on 77 samples of Galema range magmas. We interpret contrasting results between two modeling approaches as evidence for magma ponding subsequent to melt generation. Trace element models of melt generation reveal melting conditions of TP=1418-1450°C at 2.9-3.2 GPa, some ~68-100°C above ambient. In contrast, Si/Mg activity thermobarometry, which probes the point at which these magmas last re equilibrated with the mantle, yielded broadly similar temperatures (1435-1474°C) but at lower pressures (2.1-2.6 ± 0.2 GPa: 78-89 km depth); these results are broadly parallel to contemporaneous magmatism on the western rift margin in the Akaki Magmatic Zone. We interpret these results as evidence for magma stalling at a thermo-mechanical boundary to ascent: the lithosphere-asthenosphere boundary. The Ethiopian continental lithosphere has therefore remained relatively thick late into the rifting process, with important potential implications for late-stage decompression melting prior to the onset of seafloor spreading.
AU  - Chiasera,B
AU  - Rooney,T
AU  - Bastow,I
AU  - Yirgu,G
AU  - Grosfils,E
AU  - Ayalew,D
AU  - Mohr,P
AU  - Zimbelman,J
AU  - Ramsey,M
DO  - 10.1016/j.lithos.2021.106494
EP  - 16
PY  - 2021///
SN  - 0024-4937
SP  - 1
TI  - Magmatic rifting in the Main Ethiopian Rift began in thick continental lithosphere; the case of the Galema range
T2  - Lithos
UR  - http://dx.doi.org/10.1016/j.lithos.2021.106494
UR  - https://www.sciencedirect.com/science/article/pii/S0024493721005375?via%3Dihub
UR  - http://hdl.handle.net/10044/1/91876
VL  - 406-407
ER  -
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