板块构造样式的转变与地球深部碳循环的开始

地球深部碳循环不仅会影响地幔的物质组成、物理化学性质和岩浆作用，同时也会显著影响全球气候变化和地球的宜居性。沉积碳酸盐岩随板块俯冲作用进入地幔的过程是驱动地球深部碳循环的最重要环节。但是在地球早期的太古宙，高热的地幔条件使得板块俯冲作用不能像现代一样持续性的进行，并且会使俯冲的碳酸盐岩在浅部发生完全脱碳作用而不能进入深部地幔，阻碍深部碳循环的进行。进入古元古代以后，随着地幔温度的降低，持续性板块俯冲作用开始，沉积碳酸盐岩才有可能大规模俯冲进入地幔。然而，碳酸盐化上地幔形成的具体时间和相关证据目前尚未确定。本项目将通过对华北克拉通新太古代-古元古代的基性岩浆岩开展系统的Mg-Zn同位素研究，找到碳酸盐化上地幔形成的证据，限定地球深部碳循环全面开始的时间，并探讨深部碳循环与板块构造样式的转变以及大氧化事件的关系，以期为地球宜居性的演化过程研究提供重要的约束。

Earth’s deep carbon cycle not only affect the composition, physical-chemical property of the mantle and the relevant magmatism but also influence the global climate change and Earth’s habitability. The subduction of sedimentary carbonates into the mantle is the most important episode driving the whole process of Earth’s deep carbon cycle. However, the super-hot mantle in the Archean inhibited the plate subduction proceeding in a continuous style like the modern-style subduction. Meanwhile, the hot mantle temperature resulted in the complete decarbonization at shallow depth and impeded the deep carbon cycle. Subsequently in the Paleoproterozoic, the descending of mantle temperature resulted in the onset of continuous plate subduction and eventually led to the initiation of the deep carbon cycle. The time when the sedimentary carbonates were largely subducted into the mantle is still unclear. This program will implement systematic research on the Mg-Zn isotope compositions in the Neoarchean-Paleoproterozoic mafic igneous rocks from the North China craton to find evidence for the formation of the carbonated mantle and constrain the beginning time of Earth’s deep carbon cycle. Furthermore, the relation among the deep carbon cycle, the style change of plate tectonics and the occurrence of the Great Oxidation Event will be discussed. The achievement of this program will contribute to the studies on the evolution of Earth’s habitability.