Abstract: In order to discuss the diagenetic age and regional geological structure of the cumulates in Qingshuiquan area, LA−ICP−MS zircon dating was conduct for the cumulates distributed along the south side of the main fault in the southern margin of Altyn Tagh, and the whole−rock geochemistry of the cumulates, pyroxenites, gabbros and diorites was studied. LA−ICP−MS zircon U−Pb dating of the gabbro yielded a mean ²⁰⁶Pb/²³⁸U age of (464.8±1.3) Ma. Geochemical analysis indicates that the main elements of Qingshuiquan cumulates are characterized by low TiO₂ and high Mg^#. The chondrite−normalized REE patterns are “A flat type”, which is consistent with the REE distribution of enriched mid−ocean ridge basalt (E−MORB). According to the geochemical characteristics of Qingshuiquan cumulate rock and the regional geological tectonic background, it is considered that Qingshuiquan cumulate rock is the product of homologous magma differentiation and evolution, which was formed in the extensional tectonic background, indicating that the plate collision in the southern margin of Altun in the early Middle Ordovician has basically ended.