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Negligible effect of hydrogen content on plate strength in East Africa

Nature Geoscience volume 8, pages 543–546 (2015)Cite this article

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Abstract

Continental rifting requires weak zones to exist within the strong continental plates. This weakening is thought to be induced primarily by high hydrogen contents and temperatures, as well as small grain size1,2,3. An ideal location to test models of plate strength in situ is the East African Rift4—the best exposed continental rift on Earth—which is forming adjacent to the unrifted Tanzanian Craton. Here I use magnetotelluric data to investigate electrical conductivity, and hence hydrogen content5,6, across the East African Rift and Tanzanian Craton. The images show that the Tanzanian Craton is extremely rich in hydrogen, whereas the parts of the continent that are being rifted are anhydrous, suggesting that high hydrogen content does not systematically reduce plate strength. Earlier deformation events7 may have reduced the grain size of the continental lithosphere in the East African Rift8,9 compared to the Tanzanian Craton10,11. I therefore suggest that the localization of rifting and repeated reactivation of deformed regions may not be due to hydrogen content and is instead controlled by small grain size.

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Figure 1: Map of northeast Tanzania.
Figure 2: MT models along the northern and southern profiles.
Figure 3: Mantle geotherms and olivine water contents.
Figure 4: Water-content- and grain-size-dependent viscosity for the Mozambique Belt and Tanzanian Craton.

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Acknowledgements

This work was funded by Australian Research Council grant DP0988263 and also supported by National Science Foundation grant EAR1110921. I am grateful to COSTECH, regional and district governments and locals in Tanzania for permission to carry out field work, as well as the University of Dar es Salaam, M. Khalfan and G. Boren for assistance in field work.

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  1. Lamont-Doherty Earth Observatory, Palisades, New York 10964, USA

    Kate Selway

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  1. Kate Selway
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K.S. designed the experiment, led the field work, conducted the analysis and wrote the manuscript.

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Correspondence to Kate Selway.

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The author declares no competing financial interests.

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Selway, K. Negligible effect of hydrogen content on plate strength in East Africa. Nature Geosci 8, 543–546 (2015). https://doi.org/10.1038/ngeo2453

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