Through the study on tectonic geochronology of ophiolite in Yuanyang Town of Wushan County, Gansu Province, and measured geological section, the authors discussed the formation of opiolite and significance to tectonics. The Sm-Nd isochron age of serpentine sample from ophiolite is 473 ± 23 Ma, the model age of carbonatized, silicatized meta-basalt is 546 Ma determined by U-Pb isotope dating of zircon. The study shows that the rock association of ophiolite in Wushan County is similar with Phanerozoic ophiolite, but the difference between two is that the former contain deep-water carbonates, the forming environment of ophiolite should be likely to be an initial ocean basin according to the nearly flat shape of REE chondrite normalized pattern and the discrimination diagram of trace elements of intermediate -basic rock type within the ophiolite, the ophiolite in Wushan County is the product of Paleozoic continental breakup, both of the above-mentioned ages represent the age when the continent broke up to marine basin.
