Plume-assisted intra-oceanic subduction infancy in an ancient orogen: An example from the western Kunlun

Abstract Plume-assisted subduction infancy, independent of plate tectonics and potentially applicable to Venus, is thought to have possibly occurred as an alternative architecture to the first subduction initiation in hotter early Earth in old oceanic plates. Yet, direct rock records are rarely preserved from young oceanic plates on a global scale. Here, we conduct geochemistry, zircon and titanite U-Pb-Hf isotopic analysis, and thermodynamic modeling, as well as Ti-in-zircon and Zr-in-titanite thermometers to reconstruct the pressure-temperature-time history of high temperature-low pressure granulite-facies rocks in the western Kunlun orogen. Relevant data show that they represent ocean island basalts (OIB) and were buried to ~20–25 km, reaching 820–920 °C at ca. 200 Ma, and subsequently exhumed to ≤15 km during early cooling to ~650 °C at ca. 185 Ma. Incorporating extensive existing data, plume-assisted intra-oceanic subduction infancy is proposed for the Paleo-Tethys ocean during the Early Jurassic to Late Triassic, highlighting the significance of natural exposure of scarce OIB-type metamorphic soles in offering a glimpse of fossil plume-assisted intra-oceanic subduction infancy in the cooling late Earth.