Fig. 4

Europium isotopic signatures of the mafic volcanic rocks. variation diagram of δ¹⁵³Eu versus (a) LOI; (b) Fe₂O₃,;(c) TiO₂ in mafic volcanic rocks. (d) diagram of Na₂O + K₂O versus 100 (%) × K₂O/(Na₂O + K₂O)⁴⁴ for subdivision of the alkali series into K and Na subseries. A: Na-altered rocks, B: igneous spectrum, C: K-altered rocks. The oxide contents were normalized to 100% without volatiles. The yellow area indicates no Eu isotope fractionation within the error, and slightly reddish area indicates large variation of Eu isotope ratio.