Oxygen fugacity characteristics of lithospheric mantle peridotite in northern Xingmeng orogenic belt

Spinel peridotite xenoliths have been found in Cenozoic basalts from the Nuomin and Keluo areas in the northern Daxinganling. The Mg content of olivine in the mantleperidotite indicates that the upper mantle in the study area is partially refractory. According to the olivine content and Fo diagram, a part of peridotite xenoliths fell in the Archean and Proterozoic mantle regions, which reveals that there are remnants of ancient lithospheric mantle in the lithospheric mantle of the study area. In the study area, harzburgite and lherzolite show high oxygen fugacity values (FMQ + 1.95-3.15), which is in sharp contrast to the low oxygen fugacity values of the relatively reduced ancient lithospheric mantle. It is possible that the Paleozoic paleo Asian Ocean and Mesozoic paleo Pacific subducted successively under the Xingmeng orogenic belt, resulting in the oxidation of the lithospheric mantle at that time. K ₂O (1% ～ 6%) is found in the reaction edge of mantle xenoliths. It is considered that the mantle in the study area has experienced multiple periods of K-rich meltactivity, and the source of K-rich melt may be related to the crust source material recycled by subduction.