ISOTOPE-GEOCHRONOLOGICAL U-Pb (SHRIMP-RG) AND GEOCHEMICAL CHARACTERISTICS OF ZIRCON FROM RARE METAL (W, Li) APLITE GRANITE OF THE MURMANSK BLOCK

Abstract

The article presents the results of geochemical and isotope geochronological investigations of zircon from aplite granite with scheelite and spodumene mineralization. The mineralized granite is of scientific interest as a possible source of matter for the world’s largest spodumene pegmatite Kolmozero deposit, and for the tungsten mineralization in the Kola metallogenic province. As of now, no data are available on the age of the spodumene pegmatite Kolmozero deposit, and the estimated age of possible ‘mother’ granites is 2.7 to 1.9 Ga. Zircons from the studied granite are characterized by internal inhomogeneity, with less altered central parts and intensely altered outer parts. Uranium content in zircon is changeable as well, being 2–3 times higher in the altered parts of the grains. Zircons are of two geochemical types – magmatic and metasomatic. New isotope geochronological U-Pb data for zircon indicate the 2723 ± 11 Ma age of crystallization of the aplite granite, and 2207 ± 15 Ma age of alteration and, probably, of the formation of spodumene and scheelite mineralization. These figures may indicate the age of the rare metal spodumene pegmatite in the Kolmozero deposit.