Abstract: During the Early Paleozoic, the northern Qaidam Basin (NQB) tectonic belt underwent a transition from oceanic subduction to continental subduction, resulting in the formation of the renowned ultrahigh-pressure metamorphic belt along the northern margin of the Qaidam Basin. The conclusion of orogenic activities and crustal extension was marked by the deposition of molasses, as evidenced by the Maoniushan Formation. However, the commencement of crustal extension remains a topic of debate. The utilization of volcanic and intrusive rocks as probes of deep-earth rocks can offer crucial limitations for constraining crustal activities. This study presents the implementation of LA-ICP-MS zircon U-Pb geochronology and Lu-Hf isotope analyses on volcanic rocks and intrusive granites, which were initially classified as Devonian, in the Gahainanshan region located in the eastern portion of NQB. The findings indicate that the dacite of the Mauniushan Formation has a zircon U-Pb age of 423 Ma, whereas the intrusive granite has a U-Pb age of 370 Ma. This suggests that the volcanic eruption occurred during the Late Silurian period, while the intrusive granite crystallized during the Late Devonian period. The Zircon Lu-Hf isotope analysis indicates that the Late Devonian dacite has a concentrated εHf(t) range of -12 to -8 and a two-stage Hf model age between 2.15-1.93Ga, indicating its derivation from ancient crustal materials. The later intrusive granite, however, displays an εHf(t) range of 3-11 and a two-stage Hf model age between 0.8-1.1Ga, suggesting that it mainly originated from the partial melting of new crustal materials. After conducting a comprehensive analysis of regional geology and petrology, it can be inferred that the Late Silurian-Early Devonian period was marked by a significant orogeny caused by continental deep subduction, which resulted in the thickening of the NQB crust. This process, in turn, triggered the melting of the thickened Oulongbuluke crust, leading to the formation of volcano-magmatism. In the Late Devonian, the extensive extension caused by the delamination of the thickened crust led to the upwelling of the asthenosphere material, thereby resulting in the partial melting of new crustal material. Thus, it can be concluded that the formation time of the Maonisuhan Formation in the region is highly variable, and therefore cannot be used to represent the end of orogeny and lithosphere extension in a general sense. Only the late Devonian igneous rocks provide evidence that the northern margin of Qaidam underwent significant crustal extension.