Recent progresses in plate subduction and element recycling

Abstract

New findings on behaviours of elements and the recycling of a variety of volatile components during plate subduction have been made by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences. C–H–O fluids show unexpected immiscibility at subduction zone conditions. First principles simulations reveal that high temperature greatly enhances the tendency of calcium partitioning into silicates, which implies that CaCO3 is unlikely to be the major carbon host in Earth's deep mantle. By integrating the results from this research program and the knowledge from previous studies, a unified picture of the global deep volatile cycle is provided. Carbon is the most important element on Earth, which is the core element of life. It has major influences not only on the climate change, but also on magmatic activities. The Earth's carbon is mainly stored in the mantle and the core in its reduced form such as diamond, graphite and carbide. Based on first-principle calculations and, high pressure experiments and geophysical results so far published, it is suggested that there should be a layer of "carbonate mantle peridotite" at the bottom of the upper mantle. The carbonatized layer may have acted as the source of severe climate fluctuations and mass extinction on the Earth. These progresses provide us a better understanding on the interactions between the Earth's interior and surface through plate subduction and mantle plume.