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Crustal deformation of the eastern Tibetan plateau revealed by magnetotelluric imaging

Abstract

The ongoing collision of the Indian and Asian continents has created the Himalaya and Tibetan plateau through a range of deformation processes. These include crustal thickening, detachment of the lower lithosphere from the plate (delamination) and flow in a weakened lower crust1,2,3,4,5,6. Debate continues as to which of these processes are most significant7. In eastern Tibet, large-scale motion of the surface occurs, but the nature of deformation at depth remains unresolved. A large-scale crustal flow channel has been proposed as an explanation for regional uplift in eastern Tibet6,8,9, but existing geophysical data10,11 do not constrain the pattern of flow. Magnetotellurics uses naturally occurring electromagnetic waves to image the Earth’s subsurface. Here we present magnetotelluric data that image two major zones or channels of high electrical conductivity at a depth of 20-40 km. The channels extend horizontally more than 800 km from the Tibetan plateau into southwest China. The electrical properties of the channels imply an elevated fluid content consistent with a weak crust12,13 that permits flow on a geological timescale. These findings support the hypothesis that crustal flow can occur in orogenic belts and contribute to uplift of plateaux. Our results reveal the previously unknown complexities of these patterns of crustal flow.

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Figure 1: Map showing surface relief of the eastern Tibetan plateau and the adjacent area.
Figure 2: Electrical resistivity cross-sections for eastern Tibet.
Figure 3: Variation of thickness and fluid content (porosity) for a crustal layer with a conductance of 10,000 S.
Figure 4: Fluid content (porosity) of a 20-km-thick mid-crustal layer required to account for the conductance of profiles P1 and P4.

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Acknowledgements

The authors thank Z. J. Ma, Q. D. Deng, Y. P. Wang and D. L. Zhong for their encouragement and valuable discussions. Project EHS3D is sponsored by the China National Science Foundation grants, No. 40634025, 40374034. Reviews by M. Leech, R. Law and P. Wannamaker significantly improved this manuscript and are greatly appreciated. We thank G. McNeice and A. G. Jones for the use of their decomposition software.

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D.B. designed the project, collected and interpreted data and wrote the paper. M.J.U. processed and interpreted data and wrote the paper. M.A.M. designed the project, interpreted data and wrote the paper. X.M. and Y.S. designed the project and processed data. J.T., X.K., J.S. and C.J. designed the project and interpreted data. L.W. and C.Z. designed the project and collected data. P.X. and M.L. collected the data.

Corresponding author

Correspondence to Denghai Bai.

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The authors declare no competing financial interests.

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Bai, D., Unsworth, M., Meju, M. et al. Crustal deformation of the eastern Tibetan plateau revealed by magnetotelluric imaging. Nature Geosci 3, 358–362 (2010). https://doi.org/10.1038/ngeo830

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