Amphiboles of the Ilmenogorsky miaskite complex and metamorphic rocks of its top are studied along the section of structural borehole C-2000, which drilled 400 m of fenitized rocks of the top and 1600 m of internal parts of the complex. The composition and distribution of 20 species of amphiboles of the hornblendite, edenite, tschermakite, katophorite, cummingtonite, tremolite, richterite-ferri-winchite, hastingsite and taramite mineral groups are presented. It is shown on example of variable composition of amphiboles that the country rocks were fenitized during the formation of the miaskite complex. Amphiboles of rocks of the gneiss+amphibolite-fenite+syenite-sandyite-miaskite sequence exhibit the increasing Na, Fe, and K contents and decreasing Ca and Mg contents. Later the entire complex of igneous and metamorphic rocks underwent dynamothermal metamorphism. The formation of amphibole-bearing rocks are characterized by following thermodynamic parameters: amphibolites P = 5-6 kbar; T = 600-660 °C; gneiss P = 3.5-4.8 kbar, T = 605 °C; miaskites P = 8-9 kbar, T = 600-700 °C; altered miaskites and fenites P = 4.5-6.5 kbar, T = 600 °C. The high thermodynamic parameters of miaskites are related to the presence of phacolite structure in the core of the complex.

Figures 8. Tables 8. References 31.

Key words: amphiboles, miaskite, fenites, Ilmenogorsky miaskite complex, South Urals.

E.P. Makagonov, Institute of Mineralogy UB RAS, Miass, Chelyabinsk district, 456317 Russia; mak@mineralogy ru

V.A. Kotlyarov, nstitute of Mineralogy UB RAS, Miass, Chelyabinsk district, 456317 Russia;

E.V. Korinevsky, nstitute of Mineralogy UB RAS, Miass, Chelyabinsk district, 456317 Russia

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