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．