20.500.12556/DiRROS-22462 Mineralogy, geochemistry and genesis of low-grade manganese ores of Anujurhi area, Eastern Ghats, India Mineralogija, geokemija in geneza revnih manganovih rud z območja Anujurhi, Vzhodni Gati, Indija The 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. Članek obravnava manganove rude, ki se pojavljajo znotraj visokometamorfnih gnajsov predkambrijske supergrupe Vzhodni Gati na območju Anujurhi v zvezni deželi Odisha, Indija. Zanje so značilne konformne leče, ki vsebujejo minerale, kot so kriptomelan, romanehit, piroluzit, todorokit in pirofanit, skupaj z drugimi neprozornimi minerali, kot so grafit, goethit in ilmenit. Jalovinski minerali v teh rudah vključujejo kremen, glinenec, granat, kaolinit, apatit, silimanit, cirkon, biotit, alunit in gorceiksit. Primarni elementi prisotni v rudi so Si (16,20 %), Mn (15,06 %), Fe (11,94 %) in Al (6,6 %). Dodatno so ugotovili sledne vsebnosti P, K, Ti, Mg, Ca in Na. Povprečno razmerje Fe/Mn, ki znaša 0,81, in diagram primerjave vsebnosti Si z vsebnostmi Al v rudi z območja Anujurhi nakazuje, da feromanganovi sedimenti izvirajo iz mešanih hidrotermalnih virov. Značilnosti manganove rude, kot so odsotnost karbonatnega faciesa rude in geokemična povezava Mn-Ba skupaj z razmerji Na/Mg ter tri komponentnim diagramom CaO-Na2O-MgO rud jasno kažejo, da gre za metamorfozirano plitvomorsko do jezersko nahajališče. Po odlaganju in diagenezi so manganovi minerali prestali vsaj dve fazi ultra visoke temperature (UHT) in metamorfizma granulitnega faciesa skupaj s prikamnino. Tektonski dvig, erozija, dolga izpostavljenost atmosferskemu kisiku in pronicanju meteorne vode so privedli do supergene spremembe in remobilizacije primarnih manganovih mineralov v koloidnem stanju, čemur je sledila epigenetska zamenjava vzdolž strukturno šibkih površin kamnin granulitnega faciesa, kar je povzročilo nastanek sedanjih ležišč. To dokazujejo opazovane sekundarne zamenjave in koloidne teksture v Mn oksidih. Eastern Ghats Mobile Belt (EGMB) Anujurhi manganese ore supergene enrichment Vzhodni Gati Anujurhi manganova ruda supergena obogatitev true false true Angleški jezik Slovenski jezik Neznano 2025-05-21 09:20:11 2025-05-21 09:20:11 2025-10-24 03:51:19 0000-00-00 00:00:00 2024 0 0 str. 285-300 no. 2 vol. 67 2024 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 2024-12-16 553 0016-7789 10.5474/geologija.2024.014 220244483 1903-Article_Text-12342586-1-10-20241217.pdf 1903-Article_Text-12342586-1-10-20241217.pdf 1 FAB9B0205140759CBF4EF68B766CE8A9 49d411041db4ec22669b48b5d555153caa949c14bef0f4b4fdcde7bc338906d9 47deed76-3614-11f0-963a-001a4af901a5 https://dirros.openscience.si/Dokument.php?lang=slv&id=32456 Geološki zavod Slovenije Geologija 0 0 0