This paper reports new geochemical and isotopic data from the Cretaceous volcanic rocks of the Gan-Hang Tectonic Belt,southeast China.Two periods of basaltic eruptions((143±1.1)~(139±0.7) Ma and 105~98 Ma),each representing results of separate tectonic events,are recognized in the Gan-Hang Belt.Rock types associated with these two volcanic events exhibit significant differences in mineral assemblage and chemical compositions.For the(143±1.1)~(139±0.7) Ma basalts,~(87)Sr/~(86)Sr ratio(0.704 1~0.704 8) and Sm-Nd isotopic compositions (e(Nd)=+3.78~+4.38) suggest that the magma originated from the depleted mantle and did not mix with crustal materials.During the second episode(105~98 Ma),volcanism was accompanied by intense regional extension and by development of a series of red basins in the belt.The geochemical characteristics of these basalts exhibit both tholeiite and alkaline olivine-type,indicating inhomogeneous mixing of magma with crustal materials.The tholeiites have medium-high ~(87)Sr/~(86)Sr ratio(0.705 4~0.707 0) and low e(Nd) value(1.69~0.70),indicating that the magma originated from an undepleted mantle.The alkaline olivine basalts,on the other hand,have relatively higher ~(87)Sr/~(86)Sr ratio(0.707 6~0.708 0) and relatively lower value of e(Nd)(-6.43~-5.18),suggesting that these magmas originated from enriched mantle by mixing with subducted crustal material.Based on our comprehensive geologic analyses,we conclude that an extensional environment existed in the region from the early period of the Early Cretaceous,and the Gan-Hang Belt represents the main rift zone in SE China during these time intervals.