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.

The Mianhuakeng deposit, located within the Zhuguangshan batholith in the Nanling area, is currently recognized as the largest granite-related uranium deposit in China. A portion of the uranium ore bodies is spatially associated with NE-trending mafic veins within the granite. In this study, the field investigation, zircon U-Pb dating, S and Pb isotope analysis, and whole-rock geochemical analysis were conducted on these mafic veins to explore their crystallization age, petrogenesis, tectonic setting, and relationships with uranium mineralization. The weighted mean result of zircon U-Pb is 189 ± 3 Ma, suggesting that the mafic dyke was crystallized during the Early Jurassic. The whole-rock geochemistry and isotopes exhibit characteristics of intraplate basalts, suggesting that the mafic dykes originate from an enriched mantle source consisting of garnet–spinel lherzolite, with an estimated partial melting of 1%–5%. Mafic magmas underwent low-degree contamination from the lower crust during upwelling, induced by the extension of the lithosphere during the Early Jurassic. The analyses of pyrite sulfur isotopes in mafic samples vary between −2.9‰ and 1.8‰, significantly different from that of pyrite (−14.4‰ to −7.8‰) formed during the uranium mineralization. Furthermore, the ages of the pitchblende of 127–54 Ma are much younger than the crystallization ages of mafic dykes, indicating that the mafic magmas did not contribute to the uranium mineralization of Mianhuakeng deposit during magmatism. However, the abundant reducing minerals (e.g., pyrite, hornblende, and Fe²⁺-bearing minerals) in the mafic dykes can act as a redox barrier, reducing mobile U⁶⁺ to immobile U⁴⁺ during fluid–rock interaction, thereby facilitating uranium precipitation from the hydrothermal ore-forming fluids. The secondary fractures created by the intrusion of mafic magma probably provided favorable pathways for the movement of hydrothermal fluids.

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.