The Kolmozero deposit: A unique Li source in the European Arctic of Russia

Abstract

Tens to hundreds of pegmatite veins can accumulate within a pegmatite field. However, only a limited number of pegmatite veins can be practically valued. Hence, there is a problem of identifying rare metal pegmatites at the stage of geological prospecting and appraisal. Geochemical indicators are most impartial, reproducible and highly informative for these purposes. The Kolmozero lithium deposit is located in the Neoarchaean metagabbro-anorthozites of the Patchemvareksky massif in the junction zone of the two major regional structures of the Archaean age, i.e. the Murmansk block and the Kolmozero-Voronya Greenstone Belt of the Kola Peninsula. It is shown that pegmatites of the Kolmozero deposit with industrially valued rare metal mineralization (Be, Ta, Nb, Li) are poor in large-ion lithophile elements (LILE) (Sr and Ba) and in high charged high field strength elements (HFSE) (REE, Th, Zr). They also have low values of fractionation indexes - Mg/Li and Zr/Hf. The defined geochemical indicators have been applied to estimate feldspar pegmatites and muscovite-feldspar pegmatites that are spatially associated with rare metal pegmatites of the Kolmozero lithium deposit. The feldspar (beryllium-bearing) and muscovite-feldspar (beryllium-niobium-tantalum) pegmatites have rare metal mineralization and, like albite-spodumene pegmatites, are rich in Li, Nb, Ta, Be and depleted by Sr, Ba, Zr, Y, REE. Contents of ore elements (Li, Nb, Ta, Be) content increases from feldspar to muscovite-feldspar and albite-spodumen pegmatites. It is accompanied by a decrease in values of fractionation indexes of Zr/Hf and Mg/Li, as well as a decrease in contents of light, medium and heavy lantanoids Zr, Ba and Sr.