Late Devonian gabbro-dolerite-monzonite-granodiorite complex in the basin of the Severnaya Sosva River (Northern Urals): New data on composition, age, and geochemistry

Abstract

Subject research. Hypabyssal intrusive gabbro-dolerite-monzonite-granodiorite complex from the northern part of the Tagil megazone. Material and methods. Intrusive rocks situated among the Devonian strata of the East Tagil structural-formation zone at the North Urals were studied. Petrographic studies, silicate (XRF) analyses and determination of rare elements by ICP-MS method, study of U-Pb isotopic systematics in zircons from monzonites and quartz diorites, processing and interpretation of the data obtained using discrimination and spider diagrams, as well as indicator geochemical parameters were carried out. Results. It was found that the age and structural position of the studied rocks can correlate with the well-known Late Devonian Ivdel complex, differing from the typical composition of the latter by a significant content of rocks of medium and moderately acidic composition. The geochemical parameters demonstrate values characteristic of both suprasubduction (island-arc) and oceanic volcanites, which may indicate the formation of rocks of the studied complex in an environment of termination of the subduction process and separation of the subducted slab. The presence of significant volumes of diorites and monsodiorites is probably stimulated by contamination of crustal matter by the mantle melts. Conclusions. The obtained geological, petrographic, isotope-geochronological, and geochemical data do not contradict the model of separation of the subducted slab and the arrival of mantle highly depleted matter (close to oceanic basalts N-MORB) after the termination of the subduction process.