Distribution, morphology, composition and economic potential of ferromanganese concretions from the eastern gulf of Finland

The systematic geological surveys carried out by the All-Russian Research Geological Institute (VSEGEI) since 1980 have enabled the concretion fields to be mapped. This has led to estimates of their abundance which has enabled these concretions to be regarded as a potential economic resource. Numerous data were collected during these surveys on the distribution of the different morphologies of the concretions and the geological conditions in which they formed. Detailed descriptions of the morphology and internal structure of the concretions were carried out on board ship at more than 500 sites. The abundance of the concretions varies from 1-2 to 50 kg/m 2 . Based on the results of the geological surveys, the calculated area of the Mn-rich spheroidal concretions within the boundaries of the concretion-rich fields (average abundance about 20 kg/m 2 ) situated in the Russian sector of the Gulf of Finland is about 300 km 2 and the total weight of the ore material is estimated to be about 6 x 10 6 t (equivalent to about 1 x 10 6 t of manganese metal).