A Devonian to Carboniferous intra-oceanic subduction system in Western Junggar, NW China

► Gabbro and type I lavas with MORB and minor Nb-depletion indicate a Devonian back-arc basin. ► Type II lavas and tuff with MORB, OIB and SSZ features record a late Carboniferous ridge subduction. ► Devonian-Carboniferous intra-oceanic subduction constrains orogenic architecture of Altaids.