Composition of plagioclases in rocks of layered series ofthe platinum-bearing Vurechuaivench massif, Monchegorsky complex (Kola region)
Rundkvist T. V Pripachkin P. V., Bazay A. V.
Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2017. V. 146. N 6. P. 98-110
The PGE-bearing Vurechuaivench massif is a part of the Early Proterozoic Monchegorsk complex; it is composed of the layered series of rocks: gabbronorites, anorthosites, norites. The cumulative plagioclase is present in rocks through all the Vurechuaivench massif cross-section. According to the microprobe analysis, the cumulative plagioclase in the bottom and middle parts of the massif section is represented by labrador and bytownite with content of anorthite component from An63 to An78. In the upper part of the massif section plagioclase corresponds to labrador with An62 to An69. Norites of the Nude-Poaz massif, neighboring the Vurechuaivench massif, contain bytownite with anorthite component from An71 to An81. These data support the notion that the Vurechuaivench massif is a tectonic fragment of a larger magmatic body which included also the Nude-Poaz massif. The paper displays data of microprobe analysis on plagioclases and orthopyroxenes. Results of the orthopyroxene analyses are unique for the Vurechuaivench massif, because any fragments of relict pyroxene grains were not observed previously in its high metamorphosed rocks.
Key words: Monchegorsk complex, Vurechuaivench massif, layered intrusions, mafic rocks, plagioclase, labrador, bytownite.