Insights on the late Precambrian tectonics and its coupling with mantle dynamics | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Insights on the late Precambrian tectonics and its coupling with mantle dynamics

Lundi 06 Décembre 2021
Séminaires thème Intérieurs de la Terre et des planètes
Boris Robert
(GFZ Potsdam)
Extrait: 

Plate tectonics is one of the surface expressions of the planet's cooling and plays a fundamental role in the evolution of the surface and deep Earth processes. This mechanism, which is strongly linked to mantle dynamics, could have been operational since at least 2.5 Gyrs ago and might have evolved from an episodic to a continuous regime. The age of this transition remains highly debated and could have occurred during the late Precambrian about 750-550 Myrs ago. Paleomagnetism is a central tool to test this hypothesis as it allows to quantify continental motion through time but also to determine True Polar Wander. The latter phenomenon corresponds to the coherent motion of the crust and mantle with respect to the spin axis, and is strongly related to the large-scale structure of mantle dynamics. In this study, I will present an analysis of the paleomagnetic data for the interval 750-500 Ma and a review of the geological observations, which I have used to build a plate reconstruction model. Based on this tectonic model and simple mantle dynamic simulations, I will discuss the hypotheses of tectonic evolution during the late Precambrian. I will also discuss the potential links with the extreme changes occurring in the superficial layers of the planet such as the Snowball Earth, but also the possible occurrence of important magnetic field perturbations during this time interval.