Integrated thermodynamic and thermomechanical numerical modeling: A useful method for studying deep Earth water and carbon cycling

Abstract

The plate tectonic evolution controls the mass and energy circulation between the Earth's surface and interior, during which the volatiles (e.g., water and carbon) could also accompany the tectonic up- and down-wellings. The deep Earth injection of volatiles (ingassing mainly via subduction) can modify the physical and chemical properties of rocks and thus strongly affect the processes and dynamics of Earth's interior. On the other hand, the emission of volatiles to the Earth's surface (outgassing mainly through volcanism and rifting) can influence the evolution of atmosphere, climate and habitability. Thus, the deep water and carbon cycling plays important roles in not only the solid Earth dynamics, but also the surficial environments. The time-dependent evolution of deep Earth condition and large-scale plate tectonic reconstruction have generally been used to infer the fluxes and pathways of water and carbon cycling, as well as the resulting ocean water and atmospheric carbon evolution in the Earth's surficial reservoirs. Besides multiple observations and experiments, the integrated thermodynamic and thermomechanical numerical modeling provides as a useful way for studying deep Earth water and carbon cycling in variable tectonic settings and with different conditions. In the review, I firstly introduce the numerical method integrating thermodynamic data into thermomechanical principles. Then, several typical numerical models are introduced, which highlight, respectively, the (de)hydration in shallow lithospheric subduction channel, the deep water cycling in the upper mantle and transition zone, as well as the subduction-induced carbon cycling. Finally, the general issues about water and carbon fluxes between the Earth's interior and surface are discussed, which are less constrained issues and require further studies with possible contributions from the integrated thermodynamic and thermomechanical numerical modeling.