New data on the geochemical and mineralogical features of the main manganese- and iron-bearing ore occurrences in the Central Srednogorie Zone, Bulgaria

Article in Press
Pages: 
pp. 3-17
Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria
Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria
Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria
Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria
Abstract: 

The main goal of the present study is the characterization of the mineralogical and geochemical features of polymetallic (Mn- and Fe-bearing) nodules, lens- and layer-like bodies from different localities in the central part of the Late Cretaceous Srednogorie metallogenic zone, Bulgaria. The research is based on field studies, sampling and optical microscopy, followed by a combination of analytical techniques: XRD, SEM-EDS, ICP-OES and LA-ICP-MS methods. They define pyrolusite as the main ore mineral of the studied occurrences, while manganite, todorokite, bixbyite, sarkinite, hematite and hauerite are rarer. The most common gangue minerals are quartz, calcite and zeolites. Based on the MnO/SiO2 ratio, the established minerals are divided into two groups: manganese (i) and silica-manganese (ii) phases, respectively. Their trace element composition is dominated by a high content of V, Zn, Mo, W, Co, Ni, Cu, As, Tl and Sr, whereas some of them belong to the group of the critical raw materials for high-tech products. The measured values for Y and rare earth elements of the studied oxides and hydroxides are low compared to their concentrations in modern polymetallic nodules of the Pacific Ocean. Chondrite-normalized patterns indicated weak LREE enrichment with respect to MREEs and HREEs, which are slightly depleted. Common weak to strong negative Ce anomaly, accompanied by various Sm and Eu anomalies, is also observed. The close proximity of the Late Cretaceous volcanic rocks to the Mn- and Fe-bearing ore mineralization and some structural and textural features of the studied minerals suggest hydrothermal origin of the main Mn-Fe ore occurrences in the Panagyurishte area.

Keywords: 

manganese-iron-bearing ore, critical elements, Srednogorie Zone, Bulgaria

DOI: 
10.52321/GeolBalc.51.2.3

VOLUME 51 (2)/August 2022

Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria
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Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria
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Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria
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Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria

Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria
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Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria
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Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria

Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria
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Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria
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Interoceanmetal Joint Organization, 9 Cyryla i Metodego Str., 71-541 Szczecin, Poland
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Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 24, 1113 Sofia, Bulgaria
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Faculty of Chemistry and Pharmacy, Sofia University “St Kliment Ohridski”, 1 James Bourchier Blvd, 1164 Sofia, Bulgaria
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Maritime University of Szczecin, 1/2 Wały Chrobrego, 70-500 Szczecin, Poland