Oxygen Fugacity Evolution of the Mantle Lithosphere Beneath the North
China Craton
Abstract
Oxygen fugacity controls the behavior 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 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 results reveal 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 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 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.