T024-0014
Craton evolution: a more complex story from thermochemical imaging of the lithospheric and sub-lithospheric mantle

Thursday, 10 December 2020
Poster
Walid Ben Mansour, Macquarie University, Earth and Environmental Sciences, Sydney, NSW, Australia, Juan Carlos Afonso, Macquarie University, Earth and Environmental Sciences, Sydney, Australia, Stephen F Foley, Macquarie University, Department of Earth and Planetary Sciences, Sydney, NSW, Australia, Suzanne Yvette O'Reilly, Macquarie University, Sydney, Australia, William L Griffin, Macquarie University, Department of Earth and Planetary Sciences, Sydney, Australia, Kate Selway, Macquarie University, Department of Earth and Environmental Sciences, Sydney, NSW, Australia, Andrew Macdonald, De Beers Group of Companies, Exploration, South Africa, Johannesburg, South Africa, Nicole Januszczak, De Beers Group of Companies, Exploration, Canada, Toronto, ON, Canada and Farshad Salajegheh, Macquarie University, Earth and Planetary Sciences, Sydney, NSW, Australia
Abstract:
For many years, cratons described as a region with no deformation for a long period of time, cold and thick lithosphere (up to 200 km), depleted lithospheric mantle with a dry cratonic root and high viscosity mantle in comparison with the surrounded mantle. Recent studies from geochemistry and geophysical observations show that cratonic mantle can experiment modification (metasomatism, delamination) and the evolution of the lithospheric mantle is more complex than we generally think. To highlight this complexity, we show the results of our recent thermochemical tomography of the lithosphere and sub-lithospheric upper mantle across Central and Southern Africa (MQ_MTT_2020). This region is the results of the amalgamation of several large cratonic domain (Kalahari, Tanzanian and Congo) surrounding by orogenic belts. Our tomography, based on a multi-observable probabilistic joint inversion using geophysical and geochemical datasets, which provide new information on the present-day thermochemical structure (temperature and major elements composition) in this region. Our model provides a high-resolution model of the thermochemical structure on this continental scale in comparison with models derived from seismological observations. More than the simple observations lithospheric thickness versus hot spot tracks and volcanism, our model show that main cratonic domains (Kalahari, Tanzanian and Congo) know different chemical evolutions. In this presentation, we will discuss number of robust features that carry important implications for supporting or disproving current evolutionary models for this region and Precambrian shields.