Decoupling of U–Pb and Lu–Hf isotopes and trace elements in zircon from the UHP North Qaidam orogen, NE Tibet (China): Tracing the deep subduction of continental blocks

Eclogites and gneisses from the Yuka and Xitieshan areas in the North Qaidam orogen, NE Tibet, experienced ultrahigh-pressure (UHP) metamorphism in the early Paleozoic, when the Qaidam block subducted northwards beneath the Qilian block. U–Pb ages, trace-element patterns and Hf-isotope compositions of zircon in the two rock types were used to trace the isotopic and elemental changes within zircon during continental subduction and exhumation, and...