PGE reefs of the West-Pana layered intrusion, Kola Region, Russia: plagioclase composition as an indicator of the economic potential

Abstract

The paper summarizes the present time available data on plagioclase composition through PGE reef sequences in the West-Pana intrusion, Kola Peninsula, NW Russia. The intrusion hosts two PGE-enriched levels with a strongly different economic potential. A lower level is known as “North Reef” and contains several deposits of low-sulfide Pt-Pd ores discovered in past decades whereas an upper “South Reef” level showing high-grade mineralization in some places does not have ore bodies. Comparing the variations of anorthite content in plagioclase through the North Reef with sharp changes from An63 in the underlying unit to An86 in the reef sequence with those in the South Reef (An75 with no significant changes) it is suggested that the formation of the former directly corresponds with an early-magmatic process while the latter has a distinct late-magmatic genesis. Thus plagioclase can be considered as an indicator of the economic potential of PGE reef within the West-Pana intrusion and probably in other layered intrusions when it is necessary to choose the most promising mineralized level in the stratigraphy.