Liu He, Sun Wei-Dong, Zartman Robert, Tang Ming
Center of Deep-Sea Research, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, 266071, Qingdao, China.
Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, 266237, Qingdao, China.
Nat Commun. 2019 Jul 30;10(1):3408. doi: 10.1038/s41467-019-11329-z.
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，板块俯冲的方式随时间发生了演变。虽然连续俯冲是现代板块构造的典型特征，但早期地球可能以局部间歇性俯冲的停滞盖层构造体制为特征。这两种俯冲方式之间转变的时间对地球的冷却历史有着重要的启示。在这里，我们对跨越过去35亿年的大量镁铁质岩石地球化学数据集进行了统计分析，结果显示从约21亿年前开始，碱性玄武质岩浆作用的规模不断增大。我们认为，大陆碱性玄武岩的快速增加与约21亿年前地幔冷却增强导致的地幔熔融程度突然降低有关。这可能是连续俯冲开始的结果，连续俯冲使越来越多的冷洋壳回收到地幔中。
