Geochemistry of the Joun Abad manganese deposit, north Khash, Sistan and Baluchestan province

Manganese deposits are classified as hydrogenous, diagenetic and hydrothermal deposits based on their mineralogy, chemical composition, and tectonic setting (Hein et al., 1997). Hydrogenous manganese deposits have slowly precipitated from seawater (2-10 mm/Myr) (Ingram et al., 1990). These deposits contain iron and are poor in manganese oxide. The Mn:Fe ratio is ~1 and Ni and Cu are represented by high concentrations (>3000 ppm) (Hein et al., 1997; Usui and Someya, 1997). Diagenetic manganese deposits occur as nodules and have precipitated from hydrothermal solutions or pore water within altered sediments (Klinkhammer et al., 1982). These deposits are usually related to organic matter oxidation and formation of Mn carbonate minerals (Polgari et al., 2012). Hydrothermal manganese deposits have directly precipitated from low-temperature hydrothermal solutions (Hein et al., 1997; Ingram et al., 1990). These deposits are generally laminated and stratabound or occur as irregular bodies and epithermal veins (Hein et al., 1997). Diagenetic and hydrothermal deposits are characterized by high Mn:Fe contents and low trace metal concentrations (Hein et al., 1994; Hein et al., 1996). Although there are similarities between these two deposit types, they are mostly distinguished by their morphologic, tectonic and growth rates (Kuhn et al., 1998). The Joun Abad manganese deposit is located 16 km southeast of the Joun Abad village, 72 km north of the city of Khash in the eastern longitude of 61° 06´ 0.7ʺ and the northern latitude of 28° 51´ 2.3ʺ. This zoning is structural-sedimentary that is located in the middle part of the flysch zone of Eastern Iran. In this paper, major, trace and rare earth element compositions of ores have been used as an approach to determine the conditions of ore formation. Twenty representative ore samples (~450 g) were selected from the Joun Abad manganese deposit. Geochemical analyses were made of samples taken from different surface mineral outcrops at various locations. Crushed and grounded ores (under 200 mesh) were analyzed at the Kansaran Binaloud Laboratories, Tehran, Iran. Major oxide and trace element contents were determined by X-Ray Fluorescence (XRF) and Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES), respectively, and the REEs were analyzed using the Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) method. The Joun Abad manganese deposit is located 16 km southeast of the Joun Abad village, north of the city of Khash, and with respect to structural-sedimentary zoning in the middle part of the flysch zone of Eastern Iran. The host rocks of manganese layers are red shale, manganese mineralization is visible on the upper parts, as interlayers and/or contamination. The geometry of the ore mineral is in layered form and it is often conformable with units including red shales. The chemistry of the major elements, Mn:Fe and Si:Al ratios and the positive correlation coefficients between Al2O3, TiO2 and Fe2O3 indicate that they were affected by hydrothermal processes in a shallow environment together with entering mafic clastic materials in sedimentary basin where the ore formed. All trace element diagrams show low contents of elements such as Ni, Co and Cu in the manganese ores. The deposits of the study area in these diagrams plot in the field of hydrothermal deposits. Co:Ni, Co:Zn, LREE > HREE contents and total REE and negative Ce anomalies also indicate the role of ore-bearing hydrothermal fluid in the deposit. REE distribution patterns of the deposit are quite similar to those of hydrothermal deposits.