1. Institute of Geomechanics，Chinese Academy of Geological Sciences，Beijing 100081，China; 2. Key Laboratory of Orogenic Belts and Crustal Evolution，School of Earth and Space Sciences，MOE，Peking University， Beijing 100871，China; 3. Institute of Geology and Mineral Ｒesources，Tianjin 300170，China

Small granitic intrusions occur in the progressive metamorphic belts of the Chinese Altai orogen． SHＲIMP U-Pb analyses were performed on zircons separated from a tonalite intrusion and yielded a concordant age of 409． 6 ± 3. 7 Ma ( MSWD = 0. 93) ，restricting the emplacement and crystallization of the tonalite intrusion to the Early Devonian． Combined with the existing geological data of the contemporary large granitic plutons in the Chinese Altai orogen，the tonalite is considered to be formed together with other granitic rocks in a continental arc setting． The tonalite intrusion has consistent foliation with its country rocks，indicating the strain resulting in the regional deformation should be very strong during or after the early Devonian．