Proxying Archean subduction using Phanerozoic I-type magmatism

Modern day crustal evolution is controlled by plate tectonics. I-type magmatism dominates Phanerozoic crustal growth and has been extensively used to study modern subduction systems and slab-mantle interactions. In contrast, Archean geodynamics remain poorly constrained, with no consensus on the existence of a primitive form of plate tectonics or subduction. This uncertainty largely results from a preservation bias: most Archean crust has been destroyed, and the surviving rock record shows an overprint of billions of years of overlapping, non-mutually exclusive processes such as metamorphism or hydrothermal alteration. As a result, identifying primary geochemical signatures indicative of specific Archean geodynamic mechanisms is not straightforward. In this work, we present a viable Phanerozoic proxy to Archean geodynamics using a global assessment of geochemical and experimental data. A comparison between Phanerozoic post-collisional magmatism and the Archean sanukitoid suite reveals a conspicuous geochemical resemblance based on major and trace element criteria. This common signature is coherent with derivation from a metasomatized-mantle source. The requirement for mantle metasomatism by felsic, upper-crustal material implies a mechanism capable of juxtaposing upper crust with the lithospheric mantle, potentially through continental subduction. Although this geochemical parallel does not necessarily imply a tectonic analogy, it demands active geodynamics during the Archean capable of generating hybrid lithospheric sources. Together, these observations support the use of Phanerozoic magmatic analogues as a framework for investigating Archean geodynamic processes.