Abstract
Initiation of Mariana-type oceanic subduction zones requires rheologically strong oceanic lithosphere, which developed through secular cooling of Earth’s mantle. Here, we report a 518 Ma Mariana-type subduction initiation ophiolite from northern Tibet, which, along with compilation of similar ophiolites through Earth history, argues for the establishment of the modern plate tectonic regime 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 modern plate tectonic regime 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.
Highlights
Initiation of Mariana-type oceanic subduction zones requires rheologically strong oceanic lithosphere, which developed through secular cooling of Earth’s mantle
In the Neoproterozoic-Cambrian, during Gondwana assembly[12,13,14,15,16], as mantle potential temperature continued to decrease below ΔT = 80–100 °C and lithosphere strength further increased[17], the modern plate tectonic regime was established and marked by stable plate subduction to deep mantle and high P/T UHP metamorphic assemblages[17,18,19,20,21,22]; (Fig. 1), and the extensive mountain ranges and resultant sediment erosion[23,24]
The Munabulake ophiolite is thrust upon other units of the latest Mesoproterozoic-early Paleozoic Altyn complex along its northern margin, whereas on its southwestern margin, a NW-SE directed sinistral strike-slip ductile shear zone defines the boundary with the remainder of the Altyn Complex (Fig. 2b, c)
Summary
Initiation of Mariana-type oceanic subduction zones requires rheologically strong oceanic lithosphere, which developed through secular cooling of Earth’s mantle. This setting is characterized by the formation of a proto-arc ophiolite ( referred to as a subduction initiation ophiolite), subsequently preserved in the forearc of the resultant convergent plate margin, and contains boninites, basalts, gabbroic rocks, and mantle peridotites[29,30].
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