Study on manganese mineralization associated with colored mélange of Neyriz ophiolite from Abadeh Tashk area, Fars province: using mineralogical and geochemical data

Manganese ore deposits occurred in various types of syngenetic, diagenetic and epigenetic mineralization in association with radiolarian cherts in colored melange of Neyriz ophiolite in Abadeh Tashk area, eastern Fars Province. Microscopic study and XRD analyses show a simple mineralogy for manganese compounds in all types. Psylomelane and braunite are the primary manganese compounds in syngenetic type that are found as alternative bands with amorphous silica and quartz in a sedimentary environment. Braunite and bixbite occur in lens shape deposits, showing diagenetic type of mineralization that formed in fold hinges during diagenesis process. Pyrolusite, auororite and rancieite are major minerals of epigenetic type that formed during remobilization and reprecipitation of manganese compounds in radiolarian cherts from upper horizons as open space fillings by supergene processes. Manganese ores show low values of TiO2 (0.012-0.13 %), Fe/Mn (0.02-5.45) and Al2O3 (0.019-2.13) and high values of Si/Al (21.84-427.46). The ores contain low contents of Co (31-131 ppm), Cu (17-277 ppm) and Ni (12-193 ppm) and have negative anomalies of Ce and positive Eu, low total REE and enriched LREE compared to HREE, indicating that primary manganese compounds and host cherts formed close to mid oceanic ridges above seafloor hydrothermal fluid channels.