PETROGENESIS OF THE UTLYKTASH SYNCOLLISIONAL GABBRO COMPLEX IN THE SOUTHERN URAL: FEATURES OF MAGMA FORMATION IN THE CONTEXT OF MANTLE-CRUST INTERACTION
E.L. Kunakkuzin1, I.R. Rakhimov2, T.B. Bayanova1
1Geological Institute of KSC RAS, Apatity, Russia;
2Institute of Geology of USC RAS, Ufa, Russia
Keywords: Southern Uras, collisional basaltic magmatism, petrology, geochemistry, Nd-Sr isotopic composition, U-Pb zircon age.
Abstract
A petrological, geochemical and geochronological study of gabbro intrusions of the Utlyktash complex in the northern part of the West Magnitogorsk zone of the Southern Ural was conducted. The studied intrusions are confined to the margins of the Imangulovo syncline of syncollisional origin and its periphery. The age of Uraz gabbroic massif according new LA-ICP-MS data is 333±3 Ma. The geochemical features and Nd-Sr isotopic composition of the Utlyktash complex rocks reflect a weakly depleted mantle PM-like source for gabbroids with subsequent significant magma fractionation and minor crustal assimilation (up to 6%). Thermodynamic modeling supports the fractionation model of a single parental melt from which all the studied gabbro bodies crystallized. ID-TIMS and LA-ICP-MS U-Pb zircon dating (ranging from 0.44 to 2.73 Ga) indicates the involvement of ancient continental crust and ophiolitic material from the zone of the Main Ural Fault, along which the Magnitogorsk island-arc terrane was thrust onto Laurussia paleomargin. The geological position of the Utlyktash complex and its geochemical correlation with basalts from the central part of the Magnitogorsk megazone suggest formation during syncollisional rifting in the early Carboniferous period, preceding the assembly of the Laurasia supercontinent.
|
