We present a comprehensive geochronological, mineralogical, and geochemical study on previously unknown olivine leucitites occurring in the Maiga area of southern Tibet to examine the possibility of carbonate recycling during continental subduction. The Miocene (∼16 Ma) Maiga olivine leucitites are characterized by low SiO2 (44.6–46.3 wt%), high MgO (14.0–15.7 wt%), and ultra-calcic (CaO/Al2O3 = 1.1–1.2) compositions, along with arc-like incompatible element patterns (e.g., enrichment in large-ion lithophile and light rare earth elements, and depletion in high-field-strength elements). These rocks also have extremely radiogenic 87Sr/86Sr(i) (0.715647–0.715844), unradiogenic εNd(i) (−11.6 to −11.2) and εHf(i) (−10.5 to −10.0), and moderately radiogenic 206Pb/204Pb(i) (18.44–18.46) isotopic compositions. The studied samples are also characterized by slightly heavy O isotope ratios (clinopyroxene δ18O = +6.7‰ to +8.7‰) and relatively low water contents (0.75–1.75 wt%). The geochemical features of the Maiga olivine leucitites are compatible with an origin from a carbonated peridotite mantle source. Additionally, based on the regional tectonic evolution and mid-ocean-ridge-basalt-like Zn isotopic compositions (δ66Zn = +0.26‰ to +0.30‰), we hypothesize these magmas formed from interactions between ambient mantle peridotite and recycled Ca-rich carbonate sediments during Indian continental subduction. The transition from the neighboring Miocene lamproite-like rocks in southern Tibet to olivine leucititic magmas in Maiga is assumed to reflect the tapping of two different mantle sources. The first was modified by silicate-rich sediments, which generated lamproite-like rocks, whereas the Maiga mantle source was modified by carbonate-rich sediments. This study and previous research on other K2O-rich subduction-related magmas indicate that non-negligible amounts of carbonates can be recycled deep into the mantle during continental subduction, which may play an important role in global carbon recycling.