Structure and formation mechanism of the Nizhny Tagil dunite-clinopyroxenite massif,Central Urals |
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Authors: | V R Shmelev S S Filippova |
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Institution: | 1.Institute of Geology and Geochemistry, Ural Division,Russian Academy of Sciences,Yekaterinburg,Russia;2.Moscow Institute of Steel and Alloys,National University of Science and Technology,Moscow,Russia |
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Abstract: | The results of the structural study of the Nizhny Tagil platiniferous massif in the Central Urals are presented. This is a
classic massif of the Ural-Alaskan-type zonal dunite-clinopyroxenite complexes. The massif is characterized by a nearly concentric
vertical planar internal structure conformable to petrographic zoning (layering). The primary ultramafic rocks are distinguished
by adcumulative protogranular structure with relict euhedral olivine protocrysts and distinct linear orientation of minerals,
which was formed as a result of magmatic flow. The deformational linear and planar structures conformable to the early structural
elements were formed in the process of subsequent coaxal high-temperature ductile flow. At this stage, dynamometamorphic zoning
is formed, expressed in the change of the protogranular microstructure typical of the inner portion of the massif by porphyroclastic
and mosaic microstructures in its marginal part. The country rocks underwent conjugate high-temperature metamorphism with
the formation of hornfels and kytlymite. The structure of the massif is considered to be a result of dynamic differentiation
in the course of magmatic flow followed by high-temperature coaxal flow during intrusive and diapiric ascent of rocks to the
crustal level. |
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