Geochemical, Sr–Nd–Pb, and Zircon Hf–O Isotopic Compositions of Eocene–Oligocene Shoshonitic and Potassic Adakite-like Felsic Intrusions in Western Yunnan, SW China: Petrogenesis and Tectonic Implications

Coeval potassic adakite-like and shoshonitic felsic intrusions in the western Yunnan province of SW China are spatially and temporally associated with Eocene^Oligocene shoshonitic mafic volcanic rocks. The shoshonitic syenite and quartz monzonite intrusions are characterized by high K2O contents (4·9^6·8 wt %) and K2O/Na2O ratios (1·1^1·7), high Y (1·7^34·8 ppm) and Yb (1·50^3·16 ppm) contents, nearly flat heavy rare earth element (HREE) patterns and moderate Eu anomalies (Eu/Eu*1⁄4 0·65^0·78).The potassic adakite-like granite and quartz monzonite intrusions are characterized by enrichment in light rare earth elements (LREE), depletion in HREE and fractionated HREE patterns, high Sr (328^1423 ppm), Sr/Y (38^243) and La/Yb (23^62), and low Y