Large igneous provinces, which are characterized by prodigious volumes of basalts erupted over a short duration,are commonly attributed to hot mantle plumes. However,the source and mechanism for small- scale flood basalts are subjected to considerable debate.In this study,we chose a case study from the Kyrgyz Tianshan orogenic belt to precisely determine their eruption ages,constrain the petrogenesis and discuss the deep dynamic processes using 40 Ar/ 39 Ar dating,mineral and whole- rock geochemistry. 40 Ar/ 39 Ar dating results show that the Uchkuduk lavas in the Kyrgyz Northern Tianshan were emplaced from 81. 5 to 84. 0 Ma,which formed earlier than the basalts from the other localities in the Kyrgyz Tianshan orogenic belt. Phenocryst minerals of olivine,Cr- spinel and clinopyroxene range from Fo 72. 5~91. 4 ,Cr #=13. 2～50. 1,Wo 47. 3~51. 3 En 35. 5~43. 2 Fs 9. 37~14. 2 ,respectively. The Uchkuduk basalts are characterized by oceanic island basalt (OIB)- like trace element distribution patterns with enrichment in LILE and HFSE and positive Pb,Sr,Nb- Ta and negative K anomalies in the primitive mantle- normalized trace element diagram,positive εNd (t) (+5. 2+5. 42) and moderately high ( 87 Sr/ 86 Sr)i (0. 7038～0. 7047) and ( 206 Pb/ 204 Pb)i(18. 231~18. 339)isotopic compositions, indicating an enriched asthenospheric mantle source.The olivine phenocrysts have high NiO and Fe/Mn,and low CaO contents,which are typical of the olivines crystallized from melts derived from pyroxenitic mantle source. Besides,calculated primary compositions of the Uchkuduk basalts have compositions close to L+Ol+Cpx+Grt cotectic,and they also have high FeOT (11. 2%～11. 7%),TiO2 (2. 01%～2. 12%)contents, suggesting a mainly garnet pyroxenite source,which may have been formed by the solid- state reaction between recycled oceanic crustal materials and their surrounding peridotite during earlier subduction events.The high mantle potential temperature calculated from the primary magma of the Uchkuduk basalts is comparable to the thermal anomalies of the peripheral part of a mantle plume.We proposed that low degrees of partial melting of upwelling mantle plume could be a possible mechanism to explain the Late Cretaceous- Paleogene small- scale flood basalts in the Kyrgyz Tianshan orogenic belt and neighboring areas.