Abstract:
The tectonic transition that occurred around 2.5 Ga represents one of the most significant geological events in Earth's history, shaping the early processes of continental growth and cratonization. As the dominant component of the Archean continental crust, TTGs provide valuable insights into the dynamic mechanisms of Archean plate tectonics. However, the lack of data on the pressure−temperature (
P−
T) conditions during the water−bearing melting processes of TTGs limits our ability to fully identify the tectonic mechanisms involved. This study investigates the 2.5 Ga TTGs in the Zhongtiao Mountains, using 2.5 Ga metabasalt from Wenjiapo as the source rock. Quantitative forward modeling of TTG magmatism revealed that 25% water−bearing melting at a geothermal gradient of 900℃/GPa satisfies the conditions for the formation of the 2.5 Ga TTGs in the Zhongtiao Mountains. The findings suggest that these TTGs formed in a warm subduction environment, indicating that by 2.5 Ga, the North China Craton had already developed a horizontal growth mechanism, consistent with global plate growth events. Additionally, anomalies in certain geochemical indicators suggest that the tectonic mechanism was beginning to transition toward a modern plate subduction environment.