Известия Томского политехнического университета: Инжиниринг георесурсов (Sep 2016)
Rare earth elements in the late Paleozoic coals of North Asia (Siberia, northern China, Mongolia, Kazakhstan)
Abstract
The relevance of the research is caused by the need to determine the conditions of rare earth elements (REEs) accumulation in coals, to design the model of formation and identification of criteria for predicting rare metal mineralization in coal deposits. The aim of the research is to study and evaluate the content, the patterns of distribution and REEs concentration conditions in coals from different deposits and basins of North Asia. Research methods: testing coal seams, fields and basins, formed in various geological and geochemical environments; analytical studies by INAA, ICP-MS; processing the results by mathematical statistics methods. Results. Coals of northern Asia are characterized by contents of REEs close to the coal Clark. Higher levels of the REEs content are typical for coals of northern China, Hurengol and Hotgor coalfields in eastern Mongolia and Kurai coalfield in southern Siberia. The individual coal seams or areas of ones enriched by REEs are set within certain basins at peri-background average content of REEs. Mechanism of REEs concentration in coal seams is caused by the peculiarities of nutrition composition of ancient peat accumulation basin with almost synchronously forming of volcanism and hydrogeochemistry features of the region. Epigenetic processes lead to redistribution of REEs without impacting significantly their content in fields and coal seams. Formation of anomalies and complex rare metal ores is caused by the presence of specialized arrays of rocks rich in REEs among the underlying sediments or, more often, by almost synchronously forming of volcanic alkali or acid compositions together with coal accumulation. Convertion of paleo-ashes in aggressive environment conditions of peat fields results in removal and redeposition of REEs near tonsteins with formation of contrasting anomalies. In some cases, these complex anomalies may be of industrial interest.
