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Trace and rare earth element geochemistry of the Oligocene Nikopol stratiform manganese oxide-hydroxide ores, Ukraine
  • Ahmet SASMAZ,
  • Vasyl M Zagnitko,
  • Bilge SASMAZ
Firat University

Corresponding Author:asasmaz@gmail.com

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Vasyl M Zagnitko
Taras Shevchenko National University of Kyiv
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Fırat University
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The Nikopol manganese deposit is one of the world’s largest deposits among the sedimentary manganese deposits. The Nikopol Oligocene basin is located between the Azov crystalline massif and the Ukrainian shield. Nikopol Ore horizon is traced in a thickness varying from several cm to 4.5 m and a single stratum from the west to the eastwards to about 250 km and separated to three different units; carbonate, mixed carbonate-oxide, and oxide ore. The oxide ores can contain the concretion or earthy masses bigger than 25 cm, sometimes with remnants of carbonate or carbonate-oxide textures. The manganese oxide-hydroxide ores were analyzed for major oxides, trace and rare earth elements (REE) using ICP-MS. The PAAS-normalized REE patterns of the Nikopol manganese oxide ores have similar trends and show MREE and HREEs enrichments. The Ce/Ce* values of manganese oxide-hydroxide ores collected from the study area vary from 0.88 to 1.43, indicating that ore-forming rocks were primarily marine chemical or biogenic deposit. The Eu/ Eu* anomalies of the manganese oxide-hydroxide ores are close to 1. The Y concentrations vary from 9,1 to 47,1 ppm and show negative Y anomalies. Both geochemical and Pb isotope data indicate that the Nikopol manganese oxide-hydroxide ores formed rapidly within oxic/suboxic seawater as reflected by Ce anomalies close to 1 in low-oxygen fugacity in source of the hydrothermal fluids, volcanogenic input or hydrothermal contributions to seawater. Also, our results point out that the metal was transported from both a hydrothermal source in deeper water and terrestrial sources.