Boninitic blueschists record subduction initiation and subsequent accretion of an arc–forearc in the northeast Proto-Tethys Ocean

Abstract Subduction of oceanic lithosphere is a diagnostic characteristic plate tectonics. However, the geodynamic processes from initiation to termination subduction zones remain enigmatic mainly due scarcity appropriate rock records. We report first discovery early Paleozoic boninitic blueschists and associated greenschists eastern Proto-Tethyan North Qilian orogenic belt, northeastern Tibet, which have geochemical affinities that are typical forearc boninites island arc basalts, respectively. The protoliths record intra-oceanic at ca. 492–488 Ma in arc/forearc–backarc system, whereas peak blueschist facies metamorphism reflects subsequent arc/forearc complex high pressure 455 Ma. These relations therefore life circle an zone within Proto-Tethys Ocean. evolution provides analogue development Izu–Bonin–Mariana its later beneath extant Japanese margin. This finding highlights important role former upper arc/forearcs reducing likelihood preservation initial subduction-related records ancient belts.