Geochemistry and ore mineralization of Yar-Gozero moderately alkaline complex, Central Karelia

Results of mineralogical and geochemical study of the rocks from Syargozero moderately alkaline complex (Central Karelia, Ondozero-Segozero prospect) consisting from pyroxenites, gabbro, monzodiorites and syenites are reported. The rocks are enriched with alkalies, P, Ti, Rb, Ba, Sr and light rare-earth elements (LREE). Phase I is represented by pyroxenites and gabbro, a later phase - by monzodiorites and syenites. The intrusion of monzodiorites and syenites is accompanied by formation of alkaline metasomatic rocks. Ore mineralization in pyroxenites, gabbro, and metasomatic rocks is represented by magnetite, ilmenite, titanit, and apatite. Naturally occurring minerals containing PGE’s, such as keithconnite and moncheite, are also encountered. Rock epidotization, imposed on all differentiates of the complex, and occurrence of sulphides (pyrite, chalcopyrite and bornite) are associated with the effect of later albitite veins. Electrum (up to 35,28 % Ag) is associated with bornite; tsumoite, native silver, tellurium, and bismuth are less common. Sphene, epidote, Ce-epidote, orthite, and later carbonates are minerals with high concentration of rare-earth minerals (LREE).