Abstract <p>To constrain the tectonic setting of Late Triassic magmatism in the Luocang area, western Gangdese Belt, this study analyzes monzogabbros via zircon U–Pb dating, whole-rock geochemistry, Sr–Nd–Hf isotopic analysis, and mineral chemistry. Zircon U–Pb dating yields four age groups: 295 ± 4.9, 258.6 ± 1.8, 203.5 ± 2.7, 148.8 ± 3.5 Ma. Based on the analysis of its zircons, we conclude that its formation age is constrained to the Late Triassic (203.5 ± 2.7 Ma). The monzogabbros, classified as shoshonitic-series metaluminous basic rocks, exhibit geochemical characteristics of continental margin arcs – enrichment in LILEs and depletion in HFSEs, with total REEs of 188–197 ppm and no significant Eu anomaly. Isotopically, they have (⁸⁷Sr/⁸⁶Sr)ᵢ = 0.70394–0.70400, εNd(t) = +2.8…+3.1, and zircon εHf(t) = +6.9…+13.7, indicating a metasomatized depleted mantle wedge, modified by subducted sediment-derived melts and slab-derived melts.Mineralogically, Studies on amphiboles from the Late Triassic monzogabbros in the western Gangdese Belt indicate that they are similar in properties to the basic rocks in the eastern Gangdese Belt, both derived from magmas with relatively high oxygen fugacity and water content. Geochemical and mineralogical data confirm that the parental magma of monzogabbro was derived from partial melting of the metasomatized mantle wedge, and the monzogabbro formed by fractional crystallization of the parental magma. In addition, the magmas assimilated a certain amount of juvenile lower crustal materials during their ascent.</p>