The geodynamic setting leading to the formation of Earth’s first continents remains debated. Zircons preserved in Archaean granitoids record evidence of a relatively oxidizing and wet magmatic source. Subduction-related mechanisms for the formation of Archaean granitoids have been invoked to explain these signatures, suggesting an early initiation of subduction on Earth between 4.0 and 3.6 billion years ago, in the Eoarchaean era. Here I use forward petrological modelling and Monte Carlo randomization models to show that relatively oxidizing and wet magmas resembling Archaean granitoids worldwide can occur from melts derived from the partial melting of an overthickened mafic crust in a non-subduction scenario. The formation of oxidizing and wet magmatic signatures is therefore not diagnostic of continental crust generation by subduction or of subduction initiation in the Eoarchaean. Instead, the apparent observed increase in oxygen fugacity and water contents during the Eoarchaean may indicate magmatic thickening and melting of overthickened crust with time, suggesting that this process may have contributed to the development of Earth’s first continents.

导致地球第一块大陆形成的地球动力学背景仍然存在争议。太古宙花岗岩中保存的锆石记录了相对氧化和潮湿的岩浆源的证据。与俯冲相关的太古代花岗岩形成机制已被用来解释这些特征，这表明地球上的俯冲作用早在 4.0 至 36 亿年前的太古宙时代就开始了。在这里，我使用正演岩石学模型和蒙特卡罗随机化模型来表明，世界范围内类似太古宙花岗岩的相对氧化和湿润的岩浆可能是由非俯冲情况下过度增厚的镁铁质地壳部分熔融产生的熔体产生的。因此，氧化和湿岩浆特征的形成不能诊断大陆地壳通过俯冲形成或太古宙俯冲起始。相反，在太古宙期间观察到的氧逸度和含水量明显增加可能表明岩浆随着时间的推移而增厚和过度增厚的地壳融化，这表明这一过程可能促进了地球第一批大陆的发展。