Abstract: A marine volcanic rock association composed of basalt, andesite and dacite is distributed in the Sangxiu Formation in the southern part of Yamzho Yumco. It was erupted in the late Late Jurassic to early Early Cretaceous. Regional data indicate that this area was located on the passive continental margin of the supercontinent Gandwana during this period. Geochemical analysis indicates that the volcanic rocks formed in a continental-margin rift environment.