Scientific publications

The oldest (Hadean) known minerals and rocks are a few thousands of zircon crystals aged up to 4.4–4.0 Ga, metagabbro of 4.16 Ga age from the Nuvvuagittuq greenstone belt in the Superior Province, Canada, and 4.02 Ga old Acasta granitoids in the Slave Province, Canada. These data suggest that the Earth already had a core, continental and oceanic lithosphere, hydrosphere, anoxic atmosphere and magnetic field as early as in the Hadean. However, the rocks that formed at this earliest stage are too scarce to draw objective conclusions about the geodynamic processes responsible for lithospheric evolution in that period. Evidence for Meso- and Neoarchean geological evolution obtained in the past few decades suggests that plate tectonics mechanisms were already at work during those periods and that all the geodynamic settings known today already existed. Structures composed of Meso- and Neoarchean complexes are valuable for testing numerical models of early-Earth geodynamic processes because they are relatively abundant and can thus be studied geologically in detail. Paleogeodynamic reconstructions of the Paleo-and Eoarchean can only be performed through numerical simulation because geological methods are of limited applicability due to the scarcity of these structures on the Earth. Further progress in the study of the Hadean could be achieved if more matter (rocks and minerals) of this age is found. Furthermore, close attention should be given to the study of TTG-granitoids.