Institute of Geology, Karelian Research Center, Russian Academy of Sciences, Petrozavodsk, Russia:

A. M. Ruchyev, Senior Researcher, ruchyov@krс.karelia.ru

Numerous garnet ore occurrences and deposits in the Louhi, Kem and Belomorsk municipal districts of the Republic of Karelia, recognized as part of the Arctic zone of the Russian Federation, are known. These products of multi-stage endogenous metamorphism of Late Archean sialic and mafic rocks contain at least 49.2 M t of pyralspitic garnet. Garnet is considered as a promising non-radioactive integrated source of critical strategic metals, based on the new results of the study of microcomponent composition of this rock-forming mineral, a well-known concentrator of scandium and yttrium-group rare-earth elements (TR) (^YTR=Y+Sm+Eu+...+Lu). These elements are most abundant in garnet of sialic rocks occurring dominantly as various mineral facies of paragneisses (Sc₂O₃—211–521 g/t; TR₂O₃—245–608 g/t, YTR—85.5–99.8%). Garnet of some varieties of mafic (apobasic) rocks also contains elevated rare-metal concentrations (Sc₂O₃—145–147 g/t; TR₂O₃—188–341 g/t, ^YTR—94.3–98.9%). In accordance with accepted minimum economic concentrations in ores (Sc₂O₃—0.01%, TR₂O₃—0.2%), scandium is a major useful constituent and TR is an associated constituent. Forecast scandium and TR resources were estimated on the basis of new data on their average concentrations in garnet and publications on garnet reserves and resources at some of its deposits and occurrences. The garnet ore targets studied are recognized as small (Sc₂O₃ < 1000 t) and medium-sized (occurrences Udinskoye: Sc₂O₃—1088 t, associated ^YTR₂O₃—1443 t; Granatovy Prospect: Sc₂O₃—5338 t, ^YTR₂O₃—6409 t) deposits, based on their scandium resources. The geological, geographic and economic conditions of Karelia are quite acceptable for creating and developing a scandium and ^YTR raw materials base and for launching rare-metal industries. Therefore, scandium and TR reserves at already known garnet ore localities should be evaluated and attempts to find new ones should be made. An acute problem is to develop technology for economic extraction of rare metals from garnet.

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