Location of Rare-Earth Elements in Coals at the Sergeevskoe Deposit (Amur River Region)

The occurrence forms and location features of rare-earth elements in Miocene brown coals have been studied at the Sergeevskoe deposit (Amur region). Humic acids have been found to be concentrators of lanthanides, yttrium, and scandium in the Miocene brown coals. Rare-earth elements in the fraction related to humic matter reach 90 wt %, except for scandium which is 74 wt %. Scandium is 22 wt % in aluminosilicate minerals (clayey varieties, etc.). Lanthanides and yttrium do not exceed 5 wt % of the total in the ion-exchangeable, silicate, and disulfide forms. According to the electron microscopy results, the mineral part of the coal is represented mainly by barely soluble phosphate minerals. The coals of the Sergeevskoe deposit can serve as an easily enriched source of rare-earth elements.