Mineralogy, geochemistry and genesis of low-grade manganese ores of Anujurhi area, Eastern Ghats, IndiaPattnaik, Sujata (Avtor) Majhi, Satrughan (Avtor) Eastern Ghats Mobile Belt (EGMB)Anujurhimanganese oresupergene enrichmentThe Anujurhi manganese ores occur in the high-grade gneisses of the Precambrian Eastern Ghats Supergroup in Odisha, India. They are characterized by conformable lenses containing minerals such as cryptomelane, romanechite, pyrolusite, todorokite, and pyrophanite, along with other opaque minerals like graphite, goethite and ilmenite. The gangue minerals associated with these ores include quartz, feldspar, garnet, kaolinite, apatite, sillimanite, zircon, biotite, alunite, and gorceixite. The primary elements present in the ore, Si, Mn, Fe, and Al, average at 16.20 %, 15.06 %, 11.94 %, and 6.6 % respectively. Additionally, trace amounts of P, K, Ti, Mg, Ca, and Na were detected. The average Fe/Mn ratio of 0.81 and the Si versus Al plot of the Anujurhi manganese ores suggest a hydrogenous-hydrothermal mixed source for the ferromanganese sediments. The characteristics of the manganese ore bands, absence of carbonate facies of ore, and geochemical association of Mn-Ba together with Na/Mg ratios and CaO-Na2O-MgO ternary plot of the manganese ores strongly indicate that the mineralization is a metamorphosed shallow marine-lacustrine deposit. Following deposition and diagenesis, the manganese minerals underwent at least two phases of Ultra High Temperature (UHT) and granulite facies metamorphism along with the host rocks. Tectonic uplift, erosion, extended exposure to atmospheric oxygen and percolation of meteoric water led to the supergene alteration and remobilization of the primary manganese minerals in a colloidal state, followed by epigenetic replacement along the structural weak planes of the granulite facies rocks, resulting in the formation of the current deposits. This is evidenced by the observed secondary replacement and colloidal textures in the Mn oxides.20242025-05-21 09:20:11Neznano22462sl