THE FORMATION AND ORE POTENTIAL OF THE ALBITE FELSITES AT BIGGEJAVRI, KAUTOKEINO GREENSTONE BELT, FINNMARK, NORTHERN NORWAY

The Sc-U-REE Biggejavri deposit is located in the Kautokeino Greenstone Belt in Finnmark, Norway. Lithologies comprise metavolcanics and metasediments deposited during Early Proterozoic rifting and metamorphosed during a later orogenic event at ~1960-1860 Ma (e.g. Ettner et al., 1993). Complex Sc-U-REE minerals are hosted within concordant albitite bodies in high Mg amphibolites. The goal of this project is to characterize the complex mineralogy of the Biggejavri deposit in order to understand its formation. We will investigate if Sc-U-REE mineralization occurred prior to, during, or after metamorphism in order to understand mineralization in a regional context.

Amphibolites and albitites were investigated using microscopy, automated mineralogy, FE-SEM, EPMA, and LA-ICP-MS. Amphibolite units contain amphibole, biotite, chlorite, albite, carbonate, mica, metal oxides and sulfides. Most samples show banding or folding with preferred orientation of amphiboles. Grain sizes and textures vary across the formations. Albitites consist of dominantly albite with chlorite, biotite, Ti-oxides and lesser amphibole, carbonate, mica, REE minerals, and sulfides. Later carbonate veining crosscuts both units, whereas scapolitization seems to be restricted to the amphibolites.

Automated mineralogy and FE-SEM document complex zoning within the Ti-Cr-Fe-REE oxides and also identified small grains of bastnäsite-(La) randomly scattered through the albitites. Amphibole was identified as the most ubiquitous mineral across the mineralized and unmineralized areas of the deposit and therefore marked as a target for EPMA to identify chemical variations across the units. This will constrain the significance of different rock units in the formation of the Biggejavri deposit. Amphibole composition is mainly actinolite across the amphibolites and albitites, though sodic core-rim zoning can be seen in many amphibolites samples. Future work will include in situ U-(Th)-Pb dating to constrain the age of mineralization. Zircon and monazite have been identified but their textural meaning is still under consideration.