CLINOPYROXENE IN VOLCANIC-ROCKS OF THE TAGIL DEPRESSION, URAL SUPERDEEP HOLE

The composition of clinopyroxene in rocks of the upper volcanic sequen ce of the Imennovskaya Formation (0- to 430-m section of the Ural Supe rdeep Hole SD-4) allowed us to reveal the style and conditions of deep -seated and superficial magma differentiation. The volcanic rock serie s of the sequence composes the upper part of the Imennovskii Complex o f an Early Paleozoic island are on the Urals and was originated during fractional crystallization under a thick crust. A detailed study of t he compositional trends of the clinopyroxene shows that clinopyroxene composition, even when examined in thin basalt lava flows, is a good i ndicator of the normal or overturned attitude of volcanic sequences in regions with a complicated geologic structure.