Abstract
Despite the critical role of subduction in plate tectonics, the dynamics of its initiation remains unclear. High-temperature low-pressure metamorphic soles are vestiges of subduction initiation, providing records of the pressure and temperature conditions along the subducting slab surface during subduction initiation that can possibly differentiate the two end-member subduction initiation modes: spontaneous and induced. Here, using numerical models, we show that the slab surface temperature reaches 800–900 °C at ~1 GPa over a wide range of parameter values for spontaneous subduction initiation whereas for induced subduction initiation, such conditions can be reached only if the age of the overriding plate is <5 Ma. These modeling results indicate that spontaneous subduction initiation would be more favorable for creating high-temperature conditions. However, the synthesis of our modeling results and geological observations indicate that the majority of the metamorphic soles likely formed during induced subduction initiation that involved a young overriding plate.
Highlights
Despite the critical role of subduction in plate tectonics, the dynamics of its initiation remains unclear
Subduction initiation (SI) is an important factor that impacts the motion and the configuration of tectonic plates; for example, the SI events that lead to the formation of the Izu–Bonin–Mariana (IBM) subduction zone could have resulted in major changes in the Pacific plate motion[7,8]
While our modeling results indicate that SSI can lead to high-temperature conditions that are comparable to the PT records of metamorphic soles over a wide ranges of parameter values, the synthesis of the PT records, regional geological observations, and the modeling results indicate that ISI is a more common mode of SI that produces metamorphic soles
Summary
Despite the critical role of subduction in plate tectonics, the dynamics of its initiation remains unclear. One of the possible clues to differentiating the two SI modes for active and paleo subduction zones is metamorphic soles, which are thin sheets (a few to several hundred meters thick) of highly deformed high-temperature low-pressure (HT-LP) metamorphic rocks They represent oceanic crust that were scraped off from the downing going slab during SI, welded to the base of the overriding forearc lithosphere, and exhumed together as supra-subduction zone (SSZ) ophiolite complexes[27,28,29,30,31,32]. While our modeling results indicate that SSI can lead to high-temperature conditions that are comparable to the PT records of metamorphic soles over a wide ranges of parameter values, the synthesis of the PT records, regional geological observations, and the modeling results indicate that ISI is a more common mode of SI that produces metamorphic soles
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