YTTRIUM RARE-EARTH AND RARE-METAL ACCESSORY MINERALS OF LEUCOGRANITES IN THE ALEYSK ZMEINOGORSK COMPLEX (RUDNY ALTAY)

Abstract

The relevance and aim. The study of granitoids confined to the Aleysk Zmeinogorsk complex for the first time revealed the presence of rare accessory minerals of yttrium (priorite, fergusonite) in a sample spot of leucogranites of phase IV. According to the available data, these minerals are of pegmatitic, pneumatolith-hydrothermal and metasomatic origin, however their development at the magmatic stage is considered less common. The aim of the study is to reveal the origin of priorite and fergusonite in the Aleysk Zmeinogorsk leucogranites, as well as to explain the presence of yttrium and accessory rare-earth elements within the only intrusive zone. Research methods involve conventional mineralogical and petrographical methods, identification of accessory minerals and analysis of their composition using crashed samples; analytical studies were performed on an electronic scanning microscope JSM–6510LV (Jeol Ltd) fitted with an energy dispersive spectrometer INCA Energy 350+ in a laboratory of the Geology and Mineralogy Institute of the Siberian branch of the Russian Academy of Science (Novosibirsk) and X-ray fluorescence microscope (the Division for Geology, School of Earth Science and Engineering, TPU). Results. In line with earlier discovered yttrium (xenotime), rare-earth monazite, niobates (columbite, ilmenorutile), rare accessory minerals of yttrium-niobium and yttrium-titanium composition were identified in granitoids of the Aleysk Zmeinogorsk complex. Conclusions. The presence of priorite and fergusonite in a stock of leucogranites of IV intrusive phase allows the assumption that it was formed due to continuous inflow of melting rocks during successive intrusive phases. The inflow of intrusive material from the initial magma chamber served as a favorable condition for the rocks to be saturated with yttrium, rare-earth elements, and rare metals. The accessory minerals of corresponding composition occurred at the final stage of intrusion formation as a result of autometasomatism of its apical parts and selvages.

Keywords

• rudny altay
• granitoids
• accessory minerals
• priorite
• fergusonite
• xenotime
• thorite
• thorianite
• monazite