Geology and geochemical features of Early Paleozoic volcanites Sakmara and Voznesenka-Prisakmarian zones in Southern Urals

• Published in: Litosfera (Ekaterinburg. Online) no. 2; pp. 40 - 64
• Main Author: A. M. Kosarev
• Format: Journal Article
• Language: English
• Published: A.N. Zavaritsky Institute of Geology and Geochemistry 01.04.2015
• Subjects: geochemistry; geodynamics; serpentinite mйlange; southern urals; volcanism; volkanic complexes; вулканизм; вулканический комплекс; геодинамика; геохимия; серпентинитовый меланж; южный урал
• ISSN: 1681-9004; 2500-302X

The work is dedicated to one of the most interesting areas of the Southern Urals - Sakmara and Vozneseka-Cissakmarian zones which are identified with the Main Uralian Fault. The analysis of geological, facial and petrologic-geochemical data for volcanic complexes, forming the zone was made. The two main associations of volcanic rocks are sorted out: 1) continental-oceanic rift; 2) suprasubduction volcanic arc. Island arc volcanites of suprasubduction association are not discussed here. The first association (Є-S1) contains the following groups of volcanites: 1) continental subalkaline basalt trap formation (Mednogorsk and Kuragan formations) (Є1-O1); 2) transition from continental to oceanic basalts moderately alkaline and tholeiitic series (O1?-O2) in the lower part of the Polyakovka and Dergaish complexes, located respectively in the northern and southern parts of the Voznesensk-Prisakmarian zone; 3) oceanic basalts (O2-S1), forming the upper part Polyakovka and Dergaish complexes; 4) suboceanic basalts of Bauluss complex (O2), present with oceanic transient to island-slope basalts. The analysis of trace elements distribution has been done for basalts and less for intermediate volcanic rocks of the first association. According to chemical specifications of volcanic rocks and REE distributions the conclusion of intra-plate type of the first group volcanic rocks was made. Transitional and oceanic basalts were identified as trappoid-type oceanic formation. The absence of N-MORB basalts of oceanic stage may be related to the intra-continental nature Ural Ocean. Pulling of the mid-ocean ridge in subduction zone is also possible.