THE SHIFT OF CENOZOIC VOLCANOES AND THE SPREADING AND DRIFTING OF CONTINENTAL RIFTS IN THE EASTERN CHINA

Cenozoic basaltic volcanism of the eastern China continental rift system is mainly concentrated in three NE-extending narrow rift belts. From northwest to southeast, they are the Daxinganling-Taihangshan Belt, the Changbaishan-Tanlu Fault Belt and the Southeast Coast belt. In each of these belts, Quaternary basaltic volcanoes are located a-long the axial area of rift belts, whereas Tertiary basalts are distributed on each of the flanks of these belts. Similar to the distribution of basalts on mid-ocean ridge and its flanks, the earlier Tertiary basaltic volcanoes shifted outward from the axes of the rifts as a result of continental rift spreading. In addition, the axis of the Quaternary basaltic volcanoes is located in the northwest side of the Tertiary basaltic volcanoes, suggesting the continental lithosphere of the eastern China drifted southeastwards. The spreading and drifting rate of the continental rifts can be estimated respectively from the shifting distances and time interval of volcanoes. The direction of tectonic stress, which is deduced from the echelon arrangement of three NE-extending volcanic belts, suggests that the formation and spreading of the eastern China continental rift system is genetically related both to the northward movement of the India Plate and the northwestward movement of the Pacific Ocean Plate.