A Mesozoic volcanic basin is located in Liyang county, Jiangsu Province, East-ern China. Two eruptive cycles have been identified there. The Longwangshancycle consists of hornblende andesite--rhyolite and the Dawangshan cycle consistsof pyroxene andesite-dacite-rhyolite. Petrographic study shows that crystallizationof hornblende preceded that of pyroxene in the volcanic rocks, which may indicatehigher P_(H_2O) and lower f_(O_2) in the early stage of magmatism. These calc--alkaline volcanic rocks are characterized by a low TiO_2 contentand a REE distribution pattern with relative LREE enrichment and Eu negativeanomaly. The K--group element peaks and Ta and Ti valleys exist in the spidergrams of 17 elements, which have been recognized to be characteristic of subduc-tion--related magmas (Thompson et al., 1984). On the basis of the petrographicevidence and variation of major ande trace elements, it has been deduced that thefractional crystallization is a major mechanism of evolution of the Liyang volcanicrocks and that contamination of alkali--rich components might be involved in thelate stage of volcanic activity. The process has been satisfactorily simulated bythe petrological mixing calculation and the thermodynamic modelling (Nathan etal., 1978). Comparison has been carried out in rock associations and malor and traceelements between volcanic rocks from the Liyang basin and those in some typicaltectonic settings in the world. Petrological, mineralogical and trace element featuresall suggest that volcanic activities in the Liyang basin were probably relatedto the subduction of the Kula--Pacific plate at the margin of the East Asiancontinent during the Late Mesozoic.