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)

Abstract

<p>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).</p><p>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<sup>о</sup>С 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<sup>о</sup>С и 7.5-9.1 kbar  (Belyaev&Petrov, 2002) or to 650<sup>о</sup>С  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. </p><p> </p><p>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”.</p><p> </p><p>Belyaev O.A, Petrov V.P. // Apatity: GI KSC RAS. 2002. P. 195-208.</p><p>Map of the metamorphic rock mineral facies of the Baltic Shield. S.-Pb.: VSEGEI. 1992.</p><p>Kaulina T.V., Dlenizin A.A., Belyaev O.A., Kozlova N.E., Apanasevich E.A. // S.-Pb.: IPG RAS. 2003. 189-193 p.</p><p>Kozlov N.E., Ivanov A.A., Nerovich L.I. // Apatity: KSC RAS, 1990. 172 p.</p><p>Perchuk L.L.., Krotov A.V. // Petrologia. 1998. V.7. №4. P. 356-381.</p><p>Priyatkina L.A., Sharkov E.V. // Leningrad: Nauka. 1979. 127 с.</p>