Geochemistry of eclogites Beloretsk complex (the Southern Urals) and genetic nature of their protoliths
The article gives a detailed mineralogical, petrographic and petrogeochemical characteristics of eclogites of the Beloretsk metamorphic complex (BMK). It was found that the most likely the eclogite protoliths were Early-Middle Riphean basites of the Bashkir meganticlinorium. The calculations show that the maximum thermobaric parameters of eclogites formation in BMK reached: P - ≈13 kbar, T - ≈650°C. At the same time, widespread in rocks with symplectic structures who formed at P = 4.4-5.5 kbar, T = 480-500°C indicate a relatively rapid exhumation of the complex on the surface. It is concluded that the formation of para- and ortho- rocks of the Beloretsk metamorphic complex with a certain degree of conditionality can be divided into two main stages. The first stage is due to local(?) rifting, manifested at ≈730-710 million years ago. The second stage - the basic - happened during orogeny in fold area of Timanides under stress load (or stress + lithostatic pressure), which makes BMK as typical representative of metamorphic complexes collision type.