Using underexplored accessory minerals to treat the AMNESIA of the Earth’s continental crust history – AMNESIA

Delineating the evolution of the Earth’s dynamics and the interactions between the different silicate reservoirs (crust, mantle) is key to understanding planetary differentiation and the conditions of surface habitability. Today, plate tectonic processes play a major role in creating and destroying the Earth’s crust. For this reason, the Earth is unique in the solar system because such global dynamics are absent on other planets. Reconstructing the long-term evolution of the Earth is, however, extremely difficult since the Hadean record is essentially missing and most Archean rocks have experienced reworking and overprinting of their original signatures.
AMNESIA proposes a new way to interrogate rock records by linking petro-geochemical signatures to the Earth’s dynamic processes through geological time. Precious information are enclosed in several tiny accessory minerals found in a large variety of rock and these are particularly resistant to post-magmatic disturbance. The proposed approach is built on recent advances made by the PI on the geochemical characteristics (trace elements and O isotopes) of these phases and their inclusions, and is based on unique sets of samples collected on the different continents. The main objectives are to: 1) use accessory minerals to discriminate the different tectonic settings in which magmas can be generated during the different Earth periods and 2) recover geodynamic information on early Earth (subduction vs intraplate crust production) and the timing of the onset of plate tectonics.
AMNESIA will combine cutting edge geochemical measurements and petrology on natural samples to define new proxys for the study of crustal evolution, identify and determine the nature of the first continents.