ИСТИНА

Abstract. New geochemical data were obtained and the nature of the protolith of the ancient rocks of the Maksyutov eclogite-glaucophane schist complex was revealed on the basis of new XRF and ICP MS bulk-rock analyses of 18 representative eclogite samples. Geochemical data show that the protolith of the mafic eclogites of the Maksyutov complex was tholeiitic and subalkaline basalts of enriched (OIB) and depleted (N- and E-MORB) types with inherited signs of the subduction component and subsequent metasomatic changes. The presence in the lower lithotectonic unit of ancient (≥533 Ma) UHP ultramafic rocks indicates the participation in the early stage of the formation of a complex of tectonic mantle-but-crust inclusions of the ancient substratum of the region. The parameters and periodicity of the metamorphic transformations of the Maksyutov rocks during the convergence of the East European craton and the Paleo-Asian oceanic plate were established. According to the Grt-Cpx thermometry, at least four episodes of the conjugated prograde and retrograde metamorphism with maximal parameters up to 700-750 оС and Р ~ 3.5 GPa were revealed. Subsequent retrograde and repeated prograde stages of metamorphism occurred at lower parameters typical for the blueschist facies (T ~ 450-700 ° C, P ~ 1.2-1.7 GPa) and greenschist (T ~ 380-470 ° C, P ~ 0.7-1.3 GPa) facies, determining the parameters of HP exhumation and the position of the gradient of the metamorphic field.