Abstract:The noble gas isotopic and compositional data of alkali basalt, lherzolite xenolith and megacryst clinopyroxene from Kuandian area confirm the opinion that fractionation of noble gases existed during magmatism, and that the lighter noble gases such as He and Ne have much higher mobility and incompatibility than heavier ones like Kr and Xe. Therefore, the lighter noble gases are relatively concentrated in volcanics, especially in volcanics with bubbles, whereas lherzolite xenoliths have quite abundant heavier noble gases. Megacryst clinopyroxene has the lowest abundance of noble gases, probably attributed to its highp-Tgeneration. Noble gas isotopic compositions reveal that the mantle source beneath Kuandian area has an MORB_like reservoir with 3He/4He being 10 Ra (atmospheric3He/4He value) and40Ar/36Ar being 350. Lherzolite xenoliths possess 3He/4He ratios of 2.59~4.53Ra, reflecting their highp_Tdeformation and metasomatism. Volcanics have very low3He/4He ratios (0.47~0.61 Ra), indicating the contribution of radiogenic4He due probably to crust contamination. Most samples show excesses of21Ne and22Ne compared with atmospheric neon, while Kr and Xe isotopic compositions are indistinguishable from atmospheric values with only a few samples showing excesses of129Xe,134Xe and136Xe.