2013

Abstracts Travel
Program Organizing committee

Alkaline and subalkaline massifs of Karelia as sources of rare-earth elements

Dmitrieva .V., Kuleshevich L.V., Khazov R..

IG KarRC RAS, Petrozavodsk, Russia. DmitrievaA-V@yandex.ru;  kuleshev@krc.karelia.ru

 

REE (lanthanides La, Ce, Nd and Y) are used in various new technologies, prospecting of deposits and non-conventional sources of REE is of primary importance in all highly developed countries. The goal of the present study is to reveal REE-concentrating minerals in the most promising alkaline and subalkaline massifs of Karelia and in some types of metasomatic rocks.

ypes of REE occurrences in Karelia: 1 ultramafic alkaline rocks and carbonatites of the Tiksheozero and Yeletozero massifs (ΣREE 0.36 %), 2 - titanite-apatite ore of the Elisenvaara complex (0.22-1.7 %); 3 − subalkaline granites, pegmatites and metasomatic rocks of AR-PR age (0.13-0.41 %); 4 − Archean subalkaline gabbro-pyroxenites, monzonites and titanite-apatite ores of Central Karelia; 5 alkaline metasomatic rocks and some non-conventional types.

REE minerals and their associations. Most ore occurrences are complex and contain Ti, P, REE, Ba, Sr and Zr. Phosphates and carbonates are REE concentrators (Σ970-1250 ppm) in apatite ore from the carbonatites of the Tiksheozero massif. Lamproites from the Kostomuksha structure contain ΣREE 1300 ppm, Ba 2346, Sr 2950 and Zr 933. In the northern Lake Ladoga region, high quantities of REE are associated with alkaline rocks (ladogalite and toensbergite) and the Ba-Sr-P-Ti ore of the Elisenvaara complex (Kaivomäki and Raivimäki), where they are concentrated in sphene, apatite, orthite, epidote, monazite and carbonates. In the rocks of the complex ΣREE is 0.22-0.4 %, Zr is 220-940 ppm and increases in concentrates: 1-1.7 % in titanites and 0.45-1.36 % in apatites. Rapakivi granites from the Riphean Salmi massif display high REE concentrations, especially in greysens and greysenized skarns in their halo. Fluorite, uraninite, monazite and bastnaesite are encountered in greysens from the Lypikko occurrence (0.1% Y, 0.1 %Yb). Subalkaline intrusions (Panozero, Syargozero, Sharavalampi) of AR2 age are differentiated from gabbro-pyroxenites to monzonites and syenites. They contain ΣREE 308-1314 ppm, , Sr and Zr. REE are part of thorite (Ce 7 %), orthite, epidote, titanite, monazite, Ce-La-F-carbonates and apatite.

The study of the distribution pattern, mineralogy and geochemistry of highly alkaline rocks and complex ores will contribute to the discovery and forecast evaluation of Precambrian ore occurrences promising for REE in Karelia.