Metal Content of Brown Coals from the Raichikhinskoe Deposit (Priamurie, Far East): Conditions of Accumulation and Distribution and Prospects for Development

The formation of metal-bearing coalfields of the Raichikhinskoe deposit in the conjugation zone of distributive provinces of the Bureya uplift and coal-accumulation areas of the Zeya–Bureya sedimentary basin was studied. It was established that it occurred under conditions of the successive extraction of ore components from weathering crusts of the Bureya uplift, transportation, and unloading in the paleodelta of the Bureya River. These processes proceeded synchronously with volcanic activity in the Sikhote-Alin orogenic belt, which is associated with the supply of volcanic ash. The association of these events made it possible to distinguish two types of enrichment of the Raichikha coals in rare earth elements and yttrium (REY): terrigenous with the supply of REY by surface waters and combined terrigenous volcanogenic associated with the shedding and leaching of acidic and alkaline volcanic ash. The cerium group lanthanides predominate in coals and their combustion products. The largest fraction of REY was contained in fly ash (0.11% on a total weight basis). The mechanisms of accumulation of ore components at the stage of peat deposits are considered from the standpoint of the localization of trace ore components as clastogenic mineral forms and under the conditions of interaction of ore solutions with the organic environment of peat bogs. The quality of REY was assessed, and the most enriched sections of the Verkhnii layer were identified. Prospects for the extraction of lanthanides from coal are considered from the standpoint of the possible recovery of a number of rare, nonferrous, and noble metals in this process.