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Horizontally-forced SZI creates most metamorphic soles

Xin Zhou and Ikuko Wada provide us with another indication about the apparent dominance of horizontally-forced SZI over vertically-forced SZI:

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 SZI that can possibly differentiate the two end-member SZI forcings: vertically- and horizontally forced. 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 vertically-forced SZI whereas for horizontally-forced SZI, such conditions can be reached only if the age of the overriding plate is <5 Ma. These modelling results indicate that horizontally-forced SZI would be more favourable for creating high-temperature conditions. However, the synthesis of our modelling results and geological observations indicate that the majority of the metamorphic soles likely formed during horizontally-forced SZI that involved a young overriding plate.

Zhou and Wada (2021, Nature Communications)

Localities of metamorphic soles and their age.

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