Institute of Geology, Ufa Research Center, Russian Academy of Sciences, Ufa, Russia:

S. G. Kovalev, Acting Director, Doctor of Geological and Mineralogical Sciences, kovalev@ufaras.ru
S. S. Kovalev, Researcher

The article provides a detailed description of Fe-Ti mineralization in the layered (differentiated) bodies of the Misaelga complex (Southern Ural). Various morphogenetic types of iron and titanium oxides are described: segregation ‘drop’, monomineral precipitates of ilmenite, magnetite, and various ilmenitemagnetite intergrowths and decay structures. The chemical composition of magnetite (in wt.%): TiO₂ (from 0.13 to 14.27), Al₂O₃ (from 0.51 to 21.36), Cr₂O₃ (from 0.48 to 24.07), MgO (from 0.11 to 6.41), MnO (from 0.05 to 1.0), V₂O₅ (from 0.23 to 1.16), ZnO (from 0.8 to 5.78), NiO (from 0.13 to 0.73), SiO₂ (from 0.52 to 2.75), CaO (0.51) and ilmenite: Cr₂O₃ (from 0.13 to 1.27), MgO (from 0.27 to 5.5), MnO (from 0.14 to 3.51), V₂O₅ (from 0.14 to 0.37), Al₂O₃ (3.0) and NiO (1.4). It is shown that chromium and magnesium in magnetite and ilmenite are present only in the minerals of the picrite horizon, where transitional magnetite → chrommagnetite and ilmenite → picroilmenite varieties are formed as a result of heterovalent isomorphism. Based on the calculation of crystallization temperatures, it was found that segregation of the ore melt occurred at T above ~ 1200 °C; the crystallization temperature of ilmenite–magnetite intergrowths was 712–745 °С, and the decay temperature of the solid solution varied within 588–766 °С. It is concluded that the segregation and gravitational deposition of ore minerals are not antagonistic but are realized at certain stages of the evolution of the melt. Moreover, the mechanisms of localization of the ore substance in a limited volume are governed by the physicochemical parameters and thermobaric conditions of the environment of mineral formation during ore genesis existing in a particular volume of the melt during its crystallization.

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