This study focuses on the igneous rocks in the Bogda area along the southern margin of the Junggar Basin. Through geochemical analysis and zircon U-Pb dating, we reveal distinct differences in lithology and distribution of Late Carboniferous and Early Permian volcanic rocks between the northern and southern flanks of the Bogda Mountains. The findings suggest that the Late Carboniferous was characterized by post-collisional extension, while the Early Permian experienced intense extensional activity caused by lithospheric delamination. Late Carboniferous-Early Permian mafic rocks in the Bogda region exhibit significant depletion in high-field-strength elements (HFSE) such as Nb and Ta, slight depletion in Ti, and minor enrichment in Zr. The Nb/Ta and Zr/Hf ratios closely resemble primitive mantle values, reflecting typical mantle-derived magmatic characteristics. This suggests that crustal contamination was limited, while lithospheric contamination played a more dominant role. Late Carboniferous basalts show greater depletion in large-ion lithophile elements (LILE) and higher Mg# compared with Early Permian basalts. The Zr-TiO_₂ tectonic discrimination diagrams indicate that Late Carboniferous basalts exhibit MORB-like affinities, whereas Early Permian basalts are more enriched in large-ion lithophile elements and rare earth elements, showing intraplate basalt characteristics, indicating divergent dynamic mechanisms between the two stages. Following the closure of the North Tianshan Ocean in the Late Carboniferous, due to slab breakoff, post-collisional extension prevailed under a weakly extensional tectonic regime. By the Early Permian, the post-collisional extensional regime changed, and delamination of the subducted slab occurred beneath the Bogda area. With the influx of abundant slab-derived fluids, trace elements were progressively enriched in some mafic rocks, and geochemical indices of certain mafic rocks exhibited intraplate basalt characteristics. The two episodes of extension with contrasting dynamic mechanisms during the Late Carboniferous and Early Permian in the Bogda area impose important constraints on the nature of the southern margin of the Junggar Basin. 

选择准噶尔盆地南缘博格达地区岩浆岩为研究对象, 通过岩浆岩地球化学分析和锆石U-Pb定年, 揭示出博格达山南北两翼晚石炭世和早二叠世火山岩的岩性及分布具有明显的差异, 推测博格达地区晚石炭世构造活动为后碰撞伸展, 早二叠世构造活动为拆沉作用导致的强烈伸展。地球化学分析结果表明, 博格达地区晚石炭世基性岩高场强元素(HFSE)中Nb和Ta明显亏损, Ti轻微亏损, Zr轻微富集, Nb/Ta和Zr/Hf比值均接近原始地幔, 显示典型的幔源岩浆特征, 说明博格达地区晚石炭世和早二叠世基性岩的陆壳混染作用不强, 岩石圈混染作用的影响更强烈。与早二叠世玄武岩相比, 晚石炭世玄武岩更加亏损大离子亲石元素, 并且具有较高的Mg#值。Zr-TiO₂构造判别图解说明晚石炭世玄武岩具有洋中脊玄武岩特征, 而早二叠世玄武岩更加富集大离子亲石元素和稀土元素, 具有板内玄武岩特征, 说明二者动力学机制存在差异。推测北天山洋晚石炭世闭合后, 由于板片断离作用, 进入后碰撞伸展作用, 博格达地区整体上呈现弱伸展的构造背景。进入早二叠世, 后碰撞伸展的机制发生变化, 博格达地区俯冲板片发生拆沉作用, 随着大量板片流体的加入, 部分地区基性岩中微量元素逐渐富集, 部分基性岩地球化学指标显示板内玄武岩特征。博格达地区晚石炭世和早二叠世存在的两期动力机制不同的伸展作用对准噶尔盆地南缘盆地属性有重要的约束作用。