Ba-dominant fluoroaluminates from the Katugin rare-metal deposit (Transbaikalia, Russia)

Abstract

Multiphase aluminofluoride segregations were registered in aegirine–amphibole granite from the Vostochnyi massif of the Katugin rare-metal deposit. Among them are fluorides (fluorite), Ca–Na–Mg fluoraluminates (weberite, cryolite, pachnolite–thomsenolite, prosopite, gearksutite, ralstonite, and others), and Ba fluoraluminates, which had not been observed previously in this massif. Four fluoraluminates with high concentrations of Ba were found in aluminofluoride segregations: usovite Ba₂CaMgAl₂F₁₄, the most abundant phase, and three potentially new minerals (BaAlF₄(OH), BaCa₂AlF₉, and BaCa₄AlF₁₃). The chemical composition of Ba phases and the results of their Raman spectroscopic study are reported.