Jinlong Yao and colleagues provide us with new constraints on an SZI event that might mark the onset of deep subduction on the Earth:
We report a 518 Ma Mariana-type SZI ophiolite from northern Tibet, which, along with a compilation of similar ophiolites through Earth history, argues for the establishment of the modern plate tectonic regime [a.k.a. Ocean-plate tectonics] by the early Cambrian. The ophiolite was formed during the subduction initiation of the Proto-Tethys Ocean that coincided with slab roll-back along the southern and western Gondwana margins at ca. 530-520 Ma. This global tectonic re-organization and the establishment of Ocean-plate tectonics was likely controlled by secular cooling of the Earth, and facilitated by enhanced lubrication of subduction zones by sediments derived from widespread surface erosion of the extensive mountain ranges formed during Gondwana assembly. This time also corresponds to extreme events recorded in climate and surface proxies that herald formation of the contemporary Earth.
Yao et al. (2021, Nature Communications)
Reconstruction of Gondwana and subduction zones in its southern, western, and northern margins.