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The Bhavani Suture Zone in the Southern Granulite Terrane marks the zone of amalgamation of the Neoarchean Nilgiri Block and the northwestern Madurai Block in southern India. Here, we report detailed petrological, geochemical, and geochronological data on the Mettupalayam mafic-ultramafic complex within this suture zone with a view to evaluate the tectonothermal history of the Bhavani Suture Zone and adjoining crustal blocks. The metamorphosed complex includes charnockite, hornblendebiotite gneiss, mafic granulite, amphibolite, garnet-bearing mafic granulite, and dioritic gneiss along with metamorphosed banded iron formation. The mafic granulite and the dioritic gneiss occur as concordant layers of varying thickness within the hornblendebiotite gneiss. The salient geochemical features of the mafic granulite and the dioritic gneiss including the enrichment of large-ion lithophile elements and depletion of highfield-strength elements suggest a subduction-related arc magmatic setting. However, the amphibolites show MORB-related affinity, suggesting its formation from a N-MORB-related source and their accretion together with the overlying banded iron formation. The peak metamorphic conditions of the garnet-bearing mafic granulite were estimated using conventional geothermobarometers as 800-820°C/8.5-9.2 kbar, which we further confirm through phase equilibrium modelling in the Na 2 O-CaO-K 2 O-FeO-MgO-Al 2 O 3 -SiO 2 -H 2 O-TiO 2 -Fe 2 O 3 (NCKFMASHTO) system. Magmatic zircons with high Th/U ratio from the amphibolite display a well-defined discordia with an upper intercept age of 2,600 ± 38 Ma. Zircon grains from the dioritic gneiss show weighted mean 206 Pb/ 207 Pb age of 2,524 ± 6 Ma from concordant zircon spots and a comparable upper intercept age of 2,562 ± 34 Ma from discordant zircon spots, indicating protolith emplacement related to Neoarchean arc magmatism as inferred from our geochemical data. The thin overgrowth rims around the magmatic zircon grains in the amphibolite yielded an upper intercept age of 2,520 ± 20 Ma, which is comparable with the protolith crystallization age of the dioritic gneiss. Slightly younger weighted mean 207 Pb/ 208 Pb ages of 2,463 ± 27 Ma (from dioritic gneiss) and 2,422 ± 30 Ma (from amphibolite) are also obtained from the metamorphic zircon rims. These ages are correlated to the timing of high-grade metamorphism associated with final collision of the Nilgiri Block and the northwestern Madurai Block. Similar Neoarchean-Paleoproterozoic magmatism and high-grade metamorphism were

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