甘肃北山南带位于中亚造山带南部，是研究中亚造山带构造演化的重要区域，其晚古生代构造背景争议已久。为进一步探讨北山南带晚古生代构造演化，选取北山南带长山二长花岗岩体为对象，分析了其年代学和地球化学特征。研究发现二长花岗岩的LA-ICP-MS锆石U-Pb加权平均年龄为（291.1 ± 1.5）Ma，形成于早二叠世。地球化学数据显示，岩体为过铝质钙碱性高钾-钾玄质系列。SiO₂含量为72.07% ~ 72.94%，K₂ O含量为4.93% ~ 5.10%，且K₂ O > Na₂O，A1₂O₃含量为13.52% ~ 13.97%。稀土元素球粒陨石标准化曲线呈右倾，轻稀土相对富集（LREE/HREE为10.96 ~ 14.98），δEu为0.78 ~ 0.92，具弱负Eu异常。微量元素相对富集大离子亲石元素、贫化高场强元素，显著亏损高场强元素Nb、Sm、Y。根据区域构造演化及岩石学、地球化学等特征，认为其是后碰撞过程岩浆活动的产物，反映出中亚造山带南缘碰撞拼贴早于早二叠世完成。

Located in the south of the Central Asian orogenic belt, the southern Beishan belt in Gansu Province is a key area for studying the tectonic evolution of the Central Asian orogenic belt. Its late Paleozoic tectonic setting has been controversial for a long time. In order to further explore the late Paleozoic tectonic evolution of the southern Beishan belt, the geochronology and geochemical characteristics of the Changshan monzogranite body were analyzed. The analysis results show that the LA-ICP-MS zircon U-Ph weighted average age of the Changshan monzogranite is (291.1 ± 1.5) Ma, and the emplacement of the plutons occurred in the early Permian. Geochemical datas show that the plutons are high potassium calc-alkaline and peraluminous series rocks. The results show that SiO₂ ranges from 72.07% to 72.94%, K_2O ranges from 4.93% to 5.10%, and the contents of K₂O > Na₂O, A1₂O₃ ranges from 13.52% to 13.97%. The curves of chondrite-normalized REE are obviously right inclined, and the LREE are relatively enriched (LREE/HREE are 10.96 ~ 14.98), δEu are 0.78 ~ 0.92, with weak negative Eu anomaly. Trace elements are relatively enriched in LILE(large ion lithophile elements), depleted HFSE (high field strength elements), and significantly depleted in high field strength Elements Nb, Sm, Y. According to the regional tectonic setting, petrological and geochemical characteristics, the Changshan adamellite plutons are considered to be the product by post-collisional magmatic activity, reflecting the completion of the collision collage on the southern margin of the Central Asian orogenic belt in the early Permian.