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Recycled carbonate-induced oxidization of the convective mantle beneath Jiaodong, Eastern China
Lithos ( IF 2.9 ) Pub Date : 2020-08-01 , DOI: 10.1016/j.lithos.2020.105544 Lubing Hong , Yi-Gang Xu , Le Zhang , Yu Wang , Liang Ma
Lithos ( IF 2.9 ) Pub Date : 2020-08-01 , DOI: 10.1016/j.lithos.2020.105544 Lubing Hong , Yi-Gang Xu , Le Zhang , Yu Wang , Liang Ma
Abstract The redox state, often expressed as oxygen fugacity (fO2), is a fundamental parameter controlling geochemical and geodynamic processes. Recent studies have revealed highly variable convective-mantle fO2 values, but causes of the variability are poorly understood. High fO2 values of up to 1.6 log units above the Fayalite–Magnetite–Quartz (FMQ) buffer in Cenozoic Jiaodong basalts of eastern China vary as functions of whole-rock and olivine compositions, with strongly alkaline rocks being more oxidized than alkaline varieties, and with the observed fO2 variations of the basalts most likely reflecting those of the source. Recycled oceanic-crust carbonates occur throughout sources of Cenozoic basalts and may have acted as oxidants in mantle oxidation. We suggest that the melting of a carbonate-bearing peridotite source at depths of ~300 km generated the strongly oxidized alkaline basalts, whereas melting of a pyroxenite source at depths of ~100 km produced the weakly alkaline basalts, with the higher oxidation state of the deeper convective mantle likely resulting from differential melting of various components with unique fO2 values. This study provides a robust petrological link between mantle oxidation and geochemical recycling, which is key to understanding Earth's evolution and geophysical anomalies in the deep mantle.
更新日期：2020-08-01
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