The neoarchaean enderbite-granulite complex of the Central Kola block: stages of evolution (kola peninsula)

The paper presents the results of geological-petrological and isotope-geochemical researches of rocks and minerals of the Neoarchaean enderbite-granulite complex (Central Kola block). The results obtained allowed the researchers to determine the sequence of endogenous processes, P-T conditions and duration of the enderbite-granulite complex evolution within 2.73-1.81 Ga. Three stages of metamorphism have been established in gneisses of the Kola Group: (I) – early granulitic (2.73-2.72 Ga); (II) – superimposed amphibolite facies (2.57-2.55 Ga); (III) – retrograde low-temperature amphibolite facies (2.54 Ga). Stages I and II were separated by emplacement of enderbites (2.66 Ga) and formation of cummingtonite-biotite orthogneisses after enderbites (2.64 Ga). Ultrametamorphism in gneisses of the Kola Group was accompanied by injections of anatectic veins of microcline-plagioclase granite with garnet and sillimanite (2.55 Ga). The tectonomagmatic activity in this region culminated by the injection of veined leucogranites (ca. 2.50 Ga) that crosscut gneisses of the Kola Group, enderbite and cummingtonite-biotite orthogneisses. Based on Sm-Nd and Rb-Sr methods, the influence of Paleoproterozoic processes on the granulite-enderbite complex with the alteration of isotopic systems is recorded at 2.50 and 1.81 Ga ago.