CN; mso-bidi-language: AR-SA">Sifangtai complex is the largest mafic-ultramafic intrusion along the Shangdan fault in the north Qinling orogenic belt, covering an area of ~40 km2. A combined study of cathodoluminescence images (CL) and in situ LA-ICP-MS U-Pb isotope dating was carried out for zircons from the Sifangtai gabbro. The result of 400~500 Ma is consistent with the Caledonian movement in the Qinling orogenic belt, while the result of 700~900 Ma is probably related to the mantle superplume that broke up Rodinia in middle and west China during 830~740 Ma.