Oxygen fugacity evolution of the mantle lithosphere beneath the North China Craton.

Oxygen fugacity controls the behaviour of multivalent elements and compositions of C-O-H fluids in Earth's mantle, which further affects the cycling of materials between the deep interior and surface of Earth. The redox state of the mantle lithosphere of typical stable cratons has been well documented, but how oxygen fugacity had varied during craton destruction remains unclear. This study estimates the oxygen fugacity of peridotite xenoliths entrained in Mesozoic and Cenozoic basalts on North China Craton (NCC), a typical destroyed craton. The oxygen fugacity vs. Mg# of olivine reveals that the mantle lithosphere beneath the NCC experienced three stages of evolution in terms of oxygen fugacity. First, the refractory and oxidized peridotite xenoliths indicate that the lithospheric mantle experienced a high degree of melt extraction and later long-term and complicated metasomatism before craton destruction. Then, the variations of olivine Mg-number in peridotites and oxygen fugacity reveal significant metasomatism by melts originated from the shallow asthenosphere during the destruction of the NCC since the Mesozoic. The third stage may have occurred when mantle peridotites interacted with silica-undersaturated melts or fluids stemmed from the mantle transition zone where the stagnant Pacific slab underlies. This study further verifies that the asthenospheric convection induced by the roll-back of the subducted paleo-Pacific slab played a crucial role in the destruction of the NCC and helps understand the oxygen fugacity variability during the later life of the craton. [ABSTRACT FROM AUTHOR]