The Bystrinskii gabbro massif: the first data concerning composition, age and formation affiliation

Research subject. The research covered the geological position, material composition and rock age of a comparatively small (about 32 km 2 ) Bystrinskii gabbro massif. This massif underlies tectonic plate package consisting serpentinized dunits harzburgites ophiolite association in Eastern boundary Middle Urals. Methods. content petrogenic elements was measured by Х-ray fluorescence method using an multichannel spectrometer CPM-35. analysis rare-earth element contents conducted NexION 300S mass-spectrometer. rock-forming minerals studied microanalyzer CamecaSX100. determined 147 Sm- 143 Nd isotope dating. Amphibole geobaometers were used to determine depth formation. Results. According petro- geochemical features minerals, 147Sm-143Nd rocks found be 587 Ma. It shown that gabbroids are represented two petrographic varieties. predominant type is gabbrodolerites, which similar isotropic gabbros undisturbed sections terms mineral composition, structure, formation (not more than 2–3 km). mapping results showed under study largest among those described thus far. medium grained gabbroids, present lesser quantities, differ sharply from gabbrodolerites lower Fe, Ti, both rockforming (K, Na) rare (Li, Rb, Cs) alkalis, Ba, V, Y, Nb, Zr, Hf group, as well significantly higher quantities Ca, Mg Cr. their 10–12 km, corresponds upper mantle. Conclusions. obtained information demonstrates fragments levels section tectonically aligned massif: relatively shallow part deep mantle section.