TTG petrogenesis and early plate tectonics

Objective TTG (tonalite-trondhjemite-granodiorite) suites, major constituents of Archean continental crust, serve as key archives for understanding the formation and evolution of the early continental crust and related plate tectonic regimes and mechanisms. Methods This work presents a systematic review on the petrological definitions, classification schemes, experimental petrology, source characteristics, and genetic mechanisms of TTGs, with a particular focus on the relationship between TTG petrogenesis and early plate tectonics. Traditionally, high-pressure TTGs have been interpreted as evidence for Archean subduction. However, emerging paradigms, including the "mush model" and geodynamic numerical simulations, suggest that the compositional diversity of TTG can be reasonably explained by late-stage magmatic processes (e.g., crystal-melt separation) and that TTG can also be formed through non-subduction mechanisms (e.g., crustal dripping, mantle plumes). Results Recent applications of non-traditional stable isotopes (e.g., B, Si, K, Ca), big data analytics, and machine learning in the early Earth studies provided novel insights into tracing TTG source characteristics (such as the incorporation of supracrustal materials) and early tectonic settings. Conclusion This review suggests that future TTG research should further integrate petrology, geochemistry, and numerical modeling, enhance the identification of primary melt compositions, develop more robust geochemical indicators to effectively discriminate between different mechanisms (e.g., subduction vs. mantle plumes), and conduct multi-scale, interdisciplinary studies in key areas. Significance These efforts are crucial for deepening our understanding of the tectonic evolution of the early Earth and the mechanisms of continental crust growth.