The tectonic evolution of the Paleo-Asian Ocean (PAO) has been well studied, including its gradual narrowing and closure by subduction. However, aspects of the tectonic evolution of the oceanic domain remain unclear, including the exact timing and nature of the closure. The Central Asian Orogenic Belt (CAOB) was formed by the closure of the PAO and, therefore, contains information about the tectonic evolution of the oceanic domain. Here, we report a study of the petrology, geochronology, and geochemistry of the Taohaiyingzi section of the Permian Linxi Formation in Alukhorqin Banner (Northeast China) in the central part of the CAOB. A newly discovered andesitic tuff from the lower part of the Linxi Formation yields a weighted mean ²⁰⁶Pb/²³⁸U age of 262.2 ± 1.1 Ma (n = 87), indicating that the lower part of the Linxi Formation of the Taohaiyingzi section was deposited during the late Guadalupian. Provenance weathering indicators show that the sedimentary rocks of the Linxi Formation are of low maturity. Element geochemical characteristics indicate that the Linxi Formation clastic rocks were derived from eroded magmatic rocks that formed in a continental arc setting and were deposited close to the arc in a continental arc basin environment. The active margin setting was generated by the subduction of the paleo-Asian oceanic plate beneath the Xilinhot–Songliao block. The inferred palaeosalinity of the sedimentary environment changed gradually from brackish to fresh water, suggesting the end of oceanic plate subduction during the late Guadalupian, and the closure of the PAO during or after the Lopingian.

The tectonic evolution of the Paleo-Asian Ocean during the Early to Middle Permian remains a key issue in understanding the geodynamic history of the Central Asian Orogenic Belt. To address this, we conducted petrological, whole-rock geochemical, zircon U–Pb geochronological, and Hf isotopic analyses of Early Permian biotite granodiorite and Middle Permian porphyritic granite from the south-central Great Xing’an Range. Zircon U–Pb dating yields ages of 273.2 ± 1.4 Ma and 264.4 ± 1.5 Ma, indicating that these intrusions emplaced during Early and Middle Permian. Geochemical analyses show that the rocks are characterized by high SiO₂ and Al₂O₃ contents, and low MgO and CaO contents and belong to the metaluminous to weakly peraluminous series, typical of I-type granites. The rocks are enriched in light rare earth elements and large-ion lithophile elements (e.g., Rb, Ba, K), but depleted in heavy rare earth elements and high field strength elements (e.g., Nb, Ta, P, Ti), with weakly negative Eu anomalies. The Early Permian pluton exhibits low-Sr and high-Yb characteristics and thus fall in the plagioclase stability field. In contrast, Middle Permian pluton was derived from magmas generated by partial melting under high-pressure conditions and that, underwent crystal fractionation during ascent to the mid-upper crust, ultimately forming low-Sr and low-Yb type granites. All zircon ε_Hf(t) values are positive (+4.84 to +14.87), with the corresponding two-stage Hf model ages ranging from 345 Ma to 980 Ma, indicating that the magmas were predominantly derived from juvenile crustal materials accreted during the Neoproterozoic to Phanerozoic. Considering these results, we propose that the Paleo-Asian Oceanic plate continued to subduct beneath the Songliao–Xilinhot block to the north during the Early to Middle Permian, with intense subduction and crustal thickening occurring in the Middle Permian. This suggests that the south-central segment of the Great Xing’an Range was situated in an active continental marginal setting during the Early-Middle Permian.

The Central Asian Orogenic Belt (CAOB) represents a crucial area for understanding the tectonic evolution of the Paleo-Asian Ocean and surrounding orogenic systems. This study investigates the petrology, geochronology, and geochemistry of volcanic and clastic rocks from Well HFD3 in the northern Songliao Basin, which provides key insights into the tectonic development of this region. Zircon U–Pb dating of tuff samples from the Linxi Formation provides an accurate age of 251.1 ± 1.1 Ma, corresponding to the late Permian. Geochemical analyses show that the clastic rocks are rich in SiO₂ (63.5%) and Al₂O₃ (13.7%), with lower K₂O/Na₂O ratios (0.01–1.55), suggesting low compositional maturity. Additionally, the trace element data reveal enrichment in light rare earth elements (LREEs) and depletion in Nb, Sr, and Ta, with a negative Eu anomaly, which indicates a felsic volcanic arc origin. The Chemical Index of Alteration (CIA) values (53.2–65.8) reflect weak chemical weathering, consistent with cold and dry paleo-climatic conditions. These findings suggest that the Linxi Formation clastic rocks are derived from felsic volcanic arcs in an active continental margin environment, linked to the subduction of the Paleo-Asian Ocean slab. The sedimentary conditions reflect a gradual transition from brackish to freshwater environments, corresponding with the final stages of subduction or the onset of orogeny.