Occurrence and distribution of the siderophile elements in some Bulgarian coals

Abstract

Coals from fourteen Bulgarian basins and deposits were sampled. The siderophile elements Fe, Ni, Co, Mn, Cr, V, Ti and their distribution were studied in these samples. The coals have different rank and age. The studied lignite was taken from the Neogene Maritsa-West, Stanyantsi, Belibreg, Chukurovo, Sofia, Karlovo, Samokov, Kyustendil, Oranovo, Gabrovitsa, and Katrishte basins. Subbituminous coal was taken from the Paleogene Pernik Basin, bituminous coal was from the Eocene Suhostrel and Cenomanian Balkan Basins, and the Svoge Pensilvanian anthracite was also investigated. Most of the studied coals were rich in siderophile elements. Iron, Ni and Co have negative correlation with the coal ash in all coals with exception of Belibreg and Suhostrel coal. Titanium often has positive correlation with the coal ash, and Mn, Cr and V show mainly negative correlation with the ash. The following tendencies of the concentration and distribution of the siderophile elements in the studied coal were established: The concentrations of Ni and Co have similar distribution in the coal from all studied basins. The Fe has organic affinity in all studied coals and Ni and Co have organic affinity in all coals with an exception of Belibreg and Suhostrel coal. The Mn has organic affinity with an exception in the Belibreg, Chukurovo, Karlovo, Samokov, and Kyustendil coal. Cr has organic affinity with an exception of Belibreg, Chukurovo, Gabrovitsa, Kyustendil, Oranovo, and Katrishte coal. Vanadium has organic affinity in the Maritsa-West, Chukurovo, Karlovo, Sofia, Samokov, Gabrovitsa, Oranovo, and Pernik coal. Titanium has organic affinity in the Belibreg, Sofia, Karlovo, Kyustendil, and Svoge coal. The main factors for the accumulation of the siderophile elements in coals were: 1) location of the basins closely to metallogenic provinces or rocks around the basin with high concentrations of the elements; 2) good conditions for forming of organic and inorganic complexes in the ancient peat bog; 3) fracture and cleat of the coal seams in combination with the presence of infiltration solutions, which contained siderophile elements.