This block is located on the southeast coast of China from East Zhejiang to Fujian. Sporadic dark metamorphic rocks are present below the widely distributed volcanic rocks. The block was named the ‘Cathysian Block’ in 1924 by A.W. Grabau. An isotope age of 1.4–1.8 billion years was obtained from these metamorphic rocks, and other studies have revealed that the Lower Palaeozoic clastic rocks in southwestern Fujian came from the eastern side of this block. Based on this fact, it was postulated that another Precambrian continental block in addition to the Yangtze Block might have extended from Zhejiang and Fujian Provinces to the Yunkai area. To its east, the area might have been submerged under the ocean. There are still many interpretations on the boundaries, nature, and evolution of the Cathysian Block and its relationship with the surrounding continental blocks.