Petrogenesis and Geodynamic Setting of the Mamupu Lamprophyres in Eastern Tibet: Constraints From Geochronology, Geochemistry, and Sr‐Nd‐Pb Isotopes

ABSTRACT Within the Mamupu deposit (southern Yulong porphyry copper belt, eastern Tibet), the development of lamprophyre dykes serves as a prominent indicator of Late Eocene magmatism. This research presents an integrated analytical framework—comprising SIMS zircon U–Pb geochronology, whole‐rock major and trace element geochemistry, and Sr–Nd–Pb isotopic systematics—to decipher the petrogenetic evolution and geodynamic setting of these dykes. The Mamupu lamprophyres yield a crystallisation age of 37.42 ± 0.63 Ma. From a geochemical perspective, these lamprophyre dykes exhibit a distinct potassic calc‐alkaline affinity, evidenced by their elevated potassium (K 2 O = 4.98–5.28 wt%) and total alkali (K 2 O + Na 2 O = 9.27–9.53 wt%) concentrations. The trace element systematics are defined by substantial total REE abundances (ΣREE = 624.4–693.8 ppm), with multi‐element patterns showing marked enrichment in light REE (LREE) and large‐ion lithophile elements (LILEs), contrasted with a significant deficit in high‐field‐strength elements (HFSEs). The Sr–Nd–Pb isotopic systematics, characterised by initial 87 Sr/ 86 Sr ratios of 0.70555–0.70561, ε Nd ( t ) values ranging from −2.5 to −0.3, and 206 Pb/ 204 Pb ratios between 18.868 and 18.937, collectively underscore a hybrid magma source involving significant crust–mantle interaction. These geochemical features preclude an origin from simple mantle partial melting or fractional crystallisation, and they also rule out extensive crustal assimilation. Consequently, the Mamupu lamprophyres are postulated to have originated from the hybridisation of two end‐members: potassic melts derived from a metasomatised, enriched lithospheric mantle (EM II) influenced by subduction fluids, and felsic components generated by the partial melting of a thickened lower crust. The localisation of these lamprophyres was governed by an extensive strike‐slip fault developing in response to the India–Eurasia continental collision. This magmatism likely facilitated the genesis of the Mamupu Cu–Au deposit by providing essential thermal flux and potentially sourcing metallogenic components for the southern segment of the Yulong belt.