Progress in the study of subduction initiation

Subduction initiation is one of the most important processes of tectonic evolution of the Earth. Since the tectonic theory was proposed about five decades ago，studies of subduction initiation have been performed for a long time. In early time, a variety of theoretical models were proposed to describe such a process and evaluate the model controlling parameters. Some of the tectonic phenomena can be explained based on these models. Meanwhile, important physical properties of rocks were measured in laboratory, which provided a series of possible conditions for temperature, pressure and rheological parameters. Based on these preliminary results, numerical simulations were conducted to study the mechanism of subduction initiation. There have been two basic theoretical models proposed for subduction initiation. Numerical simulations investigated parameterization of the theoretical models based on the conservation of mass, momentum and energy equations. Results from numerical models discuss the roles of different controlling parameters in the evolution of subduction initiation, which explain the geological observations to some extent. However, since there are limitations on the numerical simulations and critical hypotheses for the basic models，current results remain obscure for clearly understanding the process. With the increases of geological observations and technical development for numerical simulations，it will be possible to better explain the mechanism of subduction initiation and plate tectonics. This paper is a summary of the advancements for the mechanism of subduction initiation in the last tens of years. Also, the divergent evolutionary processes of subduction initiation resulting from recent numerical simulations are discussed. Finally， possible directions for future studies of subduction initiation are proposed.