Over the Earth’s evolutionary history, the style of plate subduction has evolved through time due to the secular cooling of the mantle. While continuous subduction is a typical feature of modern plate tectonics, a stagnant-lid tectonic regime with localized episodic subduction likely characterized the early Earth. The timing of the transition between these two subduction styles bears important insights into Earth’s cooling history. Here we apply a statistical analysis to a large geochemical dataset of mafic rocks spanning the last 3.5 Ga, which shows an increasing magnitude of alkali basaltic magmatism beginning at ca. 2.1 Ga. We propose that the rapid rise of continental alkali basalts correlates with an abruptly decreasing degree of mantle melting resulting from the enhanced cooling of the mantle at ca. 2.1 Ga. This might be a consequence of the initiation of continuous subduction, which recycled increasing volumes of cold oceanic crust into the mantle.

在地球的演化历史中，由于地幔的长期冷却，板块俯冲的样式随着时间的推移而演变。虽然连续俯冲是现代板块构造的典型特征，但停滞的盖层构造带局部性的俯冲俯冲很可能是早期地球的特征。这两种俯冲方式之间的过渡时间对地球的降温历史具有重要的认识。在这里，我们对横跨最后一个3.5 Ga的大型镁铁质岩石地球化学数据集进行了统计分析，结果表明，碱性玄武岩浆岩的强度从Ca开始增加。2.1 Ga。我们认为，大陆碱性玄武岩的快速上升与地幔融化的突然降低程度有关，这是由于地幔在约40℃处的冷却增强所致。2.1 Ga。