The nature of the early Earth crust and the processes involved in its formation and stabilisation are critical questions to understand the earliest evolution of our planet, and they are yet to be resolved. Our understanding of the formation and evolution of Earth's crust is anchored on the ancient rock archives of stable cratons, but it is not clear whether or not these archives are representative of the actual crustal evolution. Geodynamic modeling and (extinct) isotope tracers provide additional constraints as well as tests for hypotheses proposed based on the rock record.

One of the most fundamental questions that is still unresolved is the timing of the onset of plate tectonics, which is a feature that is unique to the Earth among known rocky planets. Subduction zones represent the geological environment in which crustal fractionation currently takes place, but it could be argued that this particular setting is not conducive to the long-term preservation of crust due to recycling. Moreover, the style of subduction (horizontal tectonics) may have changed during early Earth history, and hence the nature of crusts generated over time. Additionally, the onset of subduction could have pre-dated global plate-tectonics, which may not have been a stable configuration on the hot young Earth.
Interpretations of the ancient rock record are strongly debated and divided among those who support uniformitarian processes throughout the Archean Eon, and those who invoke a plume-dominated, stagnant lid scenario and infracrustal differentiation with a gradual or abrupt transition to modern-style plate tectonics, likely sometime around 3 Ga.

In this Research Topic, we welcome contributions that explore the earliest part of Earth's geological history with an emphasis on the nature of the crust, its formation, and the stabilization of cratons. This includes studies of mantle-derived magmas and their fractionation, all the way through partial melting and crustal differentiation to form stable continental crust, and estimates of the continental freeboard. We welcome studies that use petrological, elemental, and/or isotopic geochemical methods to address these important questions, as well as numerical approaches and their validation against the Early Earth rock record. Additional questions that are relevant to this Research Topic include the composition of mantle-derived proto-crusts (mafic vs. ultramafic), their thicknesses, and their geochemical characteristics.

We aim to provide a broad forum for the debate and views on the early Earth crust, and hope that this Frontiers Research Topic will help to consolidate a consensus on this important subject. We particularly welcome Original Research and Review articles.

Cover Image taken in Greenland by Topic Editor Kristoffer Szilas

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