The origin of within-plate volcanism in the eastern margin of the Eurasian Plate has been attributed to the influence from the underlying Pacific stagnant slab, asthenospheric mantle flow independent of the stagnant slab, and combination of them. In this study, relatively undifferentiated alkaline basalts erupted in eastern China younger than 15 Ma, which is after the opening of the Japan Sea, were chosen to discuss spatial geochemical variation of the upper mantle beneath this area. Low-FeO alkaline basalts are depleted in FeO* and TiO
2, enriched in SiO
2, Al
2O
3, and fluid-mobile trace elements, such as Rb, Ba, K, and Pb, show enriched isotopic compositions, and are enriched in radiogenic Pb. These basalts are sporadically distributed in eastern and northeastern China. High-FeO alkaline basalts are extremely enriched in FeO* and TiO
2, depleted in SiO
2, Al
2O
3, and fluid-mobile trace elements, show depleted isotopic compositions, and are depleted in radiogenic Pb. These basalts are distributed at approximately 119°E between 30 and 40°N. These geochemical characteristics as well as geophysical investigations on the upper mantle beneath these areas suggest that fluid derived from subducted sediment and oceanic crust dehydrated at subduction zone contribute to the origin of low-FeO and high-FeO alkaline basalts, respectively.
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