The timescale of the endogenous processes and PT conditions of garnet, biotite, and plagioclase equilibrium in the mica schists and gneisses of the Korvatundra complex (Kola region)

The Korvatundra complex is situated between the granite gneisses of the White Sea complex and the rocks of the Tana belt the Kola region (Kozlov et al., 1990; Priyatkina&Sharkov, 1979) and composed of  mica gneisses, schists and quartzite schists. The metamorphism of the complex increases from south to north from the staurolite-muscovite zone to kyanite-garnet-biotite (Map of the mineral facies, 1992; Perchuk&Krotov, 1998).

The U-Pb age of igneous zircon from the metavolcanite is 2101±21 Ma (Kaulina et al., 2003). The early stages of the progressive metamorphism reflected in relict paragenesis in the southern part were under the conditions of the staurolite-chloritoid and staurolite-garnet-two-mica subfacies with 385-570^оС and 4.6-7.6  kbar (Belyaev&Petrov, 2002).  The prograde metamorphism were under the conditions of the kyanite-garnet-micas and kyanite-garnet-biotite subfacies and are reflected in the composition of newly formed, chemically non-zonal garnets, or in the similar composition newly formed garnet rim. The metamorphism stage parameters determined by the garnet indicate increasing of the temperatures and pressures to 575-615^оС и 7.5-9.1 kbar  (Belyaev&Petrov, 2002) or to 650^оС  и 7.5 kbar (Perchuk&Krotov, 1998). The time of prograde metamorphism of the Korvatundra is in the interval 1940 and 1917 Ma. Within the Korvatundra the processes of superimposed tectonometamorphism occur under conditions of the kyanite-garnet-biotite subfacies and in the north of the Korvatundra their temperatures and pressures reach of 700-750 ° C and 13-14 kbar, correspondingly. 

 

This research was funded by GI KSC RAS program 0226-2019-0052 and Fundamental Program of the Presidium of RAS section “Fundamental geological and geophysical research of the lithosphere processes”.

 

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