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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities

Lead Supervisor: Sergei Lebedev, Earth Sciences

Co-Supervisor: Nick Rawlinson, Earth Sciences

Brief summary: 
The enigmatic structure and composition of continental lithosphere will be mapped using new computational petrology tools and a combination of seismic, gravity and other data.
Importance of the area of research concerned: 
Dynamics of the lithosphere—the cold, stiff outer shell of the Earth—and its interactions with the underlying convecting mantle control earthquakes, volcanoes, and surface topography. Since the advent of plate tectonics, abundant new observations have revealed unexpected complexity of the lithosphere, raising intriguing questions regarding its most basic properties. It has become clear that the enigmatic chemical heterogeneity within the lithosphere of continents is ubiquitous and directly related to their origin and evolution, and that the continuous changes in the Earth’s surface topography, which affect the sea level, ocean currents and climate, depend on the fine, evolving balance of static and dynamic Earth-structure contributions. New computational petrology methods form the basis of a new type of petrological inversion that can accurately combine diverse geophysical and geological data. This inversion can resolve multiple properties, including the temperature and thickness of the lithosphere and its composition. The development and application of these new methods promises to solve long-standing problems relating to the lithospheric structure, composition and evolution.
Project summary : 
In this project, new methods of geophysical data inversion, powered by computational petrology, will be advanced and applied. The goal is to gain an improved understanding of the structure, composition and evolution of the Earth’s lithosphere. The geophysical datasets will include seismic surface wave data, sensitive primarily to the temperature and thickness of the lithosphere, and gravity data, sensitive to density and composition. Mantle xenolith data will provide further constraints and benchmarks. Once tuned, the methods will be applied to the construction of sophisticated, multi-parameter physical models of the lithosphere of cratons, the ancient cores of continents, using high-resolution seismic data and satellite gravity data.
What will the student do?: 
The student will start with large seismic datasets available from the supervisor and from an existing petrological inversion method. The inversion method will be advanced, in collaboration with Cambridge and international petrology experts, so as to enable modelling of compositional heterogeneity beyond the range of the current methods. Gravity data will be incorporated in the second step of the inversion so as to constrain the lithospheric composition. The methods will be applied to the lithosphere of the ancient Archean cratons, whose composition remains a matter of a heated debate.
References - references should provide further reading about the project: 
Fullea, J., S. Lebedev, Z. Martinec, N. L. Celli, 2021. WINTERC-G: mapping the upper mantle thermochemical heterogeneity from coupled geophysical-petrological inversion of seismic waveforms, heat flow, surface elevation and gravity satellite data. Geophys. J. Int., 226, 146-191,
Eeken, T., Goes, S., Pedersen, H.A., Arndt, N.T. & Bouilhol, P., 2018. Seismic evidence for depth-dependent metasomatism in cratons. Earth and Planetary Science Letters, 491, pp.148-159.
Garber, J.M., Maurya, S., Hernandez, J.A., Duncan, M.S., Zeng, L., Zhang, H.L., Faul, U., McCammon, C., Montagner, J.P., Moresi, L. & Romanowicz, B.A., 2018. Multidisciplinary constraints on the abundance of diamond and eclogite in the cratonic lithosphere. Geochemistry, Geophysics, Geosystems, 19(7), pp.2062-2086.
You can find out about applying for this project on the Department of Earth Sciences page.
Sergei Lebedev
Prof Nicholas Rawlinson
Department of Earth Sciences Graduate Administrator