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 EoceneOligocene shoshonitic mafic volcanic rocks. The shoshonitic syenite and quartz monzonite intrusions are characterized by high K 2 O contents (49⁶8 wt %) and K 2 O/Na 2 O ratios (11¹7), high Y (17³48 ppm) and Yb (150³16 ppm) contents, nearly flat heavy rare earth element (HREE) patterns and moderate Eu anomalies (Eu/Eu* 065⁰78). 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 (328¹423 ppm), Sr/Y (38²43) and La/Yb (23⁶2), and low Y