| Abstrakt: |
Introduction Manganese deposits are generally divided into hydrothermal, hydrogenous and diagenetic based on their mineralogy, tectonics and geochemical composition (Polgari et al., 2012; Schmidt et al., 2014). Hydrothermal manganese deposits have high ratios of Mn/Fe, from 0.001 to 4000 (Schultz, 2006). The ratio of Mn/Fe is higher in these deposits than in hydrogenous manganese deposits. These deposits are formed in two tectonic environments, stratabound and epithermal (Hein et al., 1997). Epithermal and stratabound hydrothermal deposits are formed along with the centers of marine environments, intra-plate reefs, or island arcs related to subduction (Hein et al., 2008; Edwards et al., 2011). These deposits also contain less Cu, Co, Pb, Zn, and Ni than hydrogenous manganese orebodies (Usui and Someya, 1997). The Salardol manganese ore deposit is located between 47°35' to 47°38' E longitudes and 34°03' to 34°06' N latitudes, 55 km west of Alashtar. This area consists of countless thrust plates that often appear as Napps, Klipps and Windows. Existing rock units in this area are based on field observations, microscopic study of rock samples, and existing geological maps, including radiolarities, breciaition limestone and Cretaceous units. Among these, as the host of mineralization with considerable expansion, the radiolarities include weathered and folded red radiolarities with layers of jaspe and clasticlime in the form of turbidite, sometimes highly tectonized and have the highest amount of manganese. Material and methods Chip Sampling selected fifty ore samples from mineralized areas. First, microscopic investigations were performed after preparing thin and polished sections. Then, additional investigations were performed on the sections in the Iran Mineral Processing Research Center by SEM method and XRD in the Kanpajooh laboratory. For geochemical studies, 20 manganese ore samples were chemically analyzed in ALS-CEMEX by the ICP-OES method to determine the abundance of basic oxides and trace and rare earth elements. Finally, various geochemical diagrams were drawn and analyzed using the obtained data and computer software. Results and discussions Mineralogy studies, XRD and SEM, indicate the presence of ore such as ramsdellite, romanechite, cryptomelane, rhodochrosite, jacobsite, franklinite, bixbyite, braunite, manganese oxide and hydroxide, pyrophanite, pyrite and chalcopyrite. The formation of manganese oxides with textures such as nodule, disseminated, scattered grain, joint filler, and stockwork and its co-occurrence with quartz and calcite indicate the submarine hydrothermal origin of the Salardol manganese deposits. The information obtained from the diagrams and ratios of the main elements, including the various SiO2/Al2O3, Si/Al, Na/Mg and Mg/Fe ratios, indicates the role of hydrothermal fluids in shallow marine or lake environments. Low levels of trace elements, such as Cu, Co, Ni and Zn, indicate that hydrothermal fluids originate from the Salardol manganese deposit. The presence of negative anomalies for Eu, Rb and K and positive for Ce, Sr, Nb, Ba, Cs and Ti indicate that this deposit is highly compatible with manganese hydrothermal deposits. Also, the normalized pattern of rare earth elements shows that the formation of the Salardol manganese deposit resulted from the activities of hydrothermal fluids. Accordingly, it can be said that the closure of Neotethys in the upper cretaceous-palaeocene and the collision of the Central Iranian microcontinent with the Arabian plate under the influence of Laramide orogeny have caused the formation of ophiolites and many transformations in this area. After that, volcanic activity with the concentration of hydrothermal systems in the direction of tectonic movements has caused the expansion of exhalative hydrothermal activity by washing elements such as Mn, Si, Pb, Zn, Cu, Au and Ba rocks and passing through existing faults; it has entered the sedimentary basin and created manganese deposits under suitable environmental conditions. [ABSTRACT FROM AUTHOR] |
