| Early Paleozoic granitoids are widely distributed in the south Altyn orogenic belt and constitute important lithological records for constraining regional tectono-magmatic evolution. However, compared with the central and eastern segments, the emplacement ages, magma source characteristics, and tectonic significance of coeval granitoid magmatism in the west-ern segment of the south Altyn orogenic belt remain poorly constrained. In this study, we present zircon U-Pb geochrono-logical, whole-rock major- and trace-element geochemical, and zircon Hf isotopic data for the Menggu’aigele pluton in the Qiemo area, western segment of the south Altyn orogenic belt. The results show that the Menggu’aigele pluton is mainly composed of quartz monzonite and monzogranite, which yielded zircon U-Pb ages of 483 Ma and 479–478 Ma, respectively, indicating emplacement during the Early Ordovician. These rocks are characterized by relatively high SiO2 contents, with average values of 62.43% for the quartz monzonite and 66.80% for the monzogranite. They also have relatively high K2O contents, with average values of 4.74% and 5.96%, respectively. Geochemically, the pluton belongs to the high-K calc-alkaline to shoshonitic series and is composed of metaluminous to weakly peraluminous I-type granitoids. The chondrite-normalized rare earth element patterns are characterized by enrichment in light rare earth elements and relative depletion in heavy rare earth elements, with negligible to weakly negative Eu anomalies. Primitive mantle-normalized trace element patterns show enrichment in large ion lithophile elements such as Rb, K, Th, and U, and depletion in Nb, Ta, Sr, P, and Ti. Zircon εHf(t) values are predominantly positive, indicating the involvement of relatively juvenile crustal materials in the magma source. Integrating petrographic, geochronological, geochemical, and Hf isotopic evidence, we suggest that the Menggu’aigele pluton formed in a subduction-related active continental margin setting. Its parental mag-mas were mainly derived from partial melting of relatively juvenile intermediate-mafic igneous rocks in the lower crust and subsequently underwent a certain degree of fractional crystallization. Combined with available regional data, Early Paleozoic granitoid magmatism in the western segment of the south Altyn orogenic belt can be divided into at least two stages: an early stage at 483–478 Ma and a later stage at 456–453 Ma. The identification of the Menggu’aigele pluton indicates that the western segment of the south Altyn orogenic belt preserves not only Late Ordovician granitoid magmatism but also Early Ordovician arc-related magmatic activity, thereby providing new petrological and geochronological constraints on the reconstruction of the Early Paleozoic tectono-magmatic evolution of this region. |