Structural Evolution of the Elikanskiy Granite–Gneiss Swell (Western Transbaikalia)

Abstract

The Elikanskiy granite–gneiss swell represents a structure, similar to Late Mesozoic Cordilleran-type metamorphic core complexes allocated within the Eravninskiy terrane of the Yenisei-Transbaikal tectonic collage, the Mongolo-Okhotskiy orogenic belt and a northern part of the Argun–Idermeg superterrane of the Central Asian orogenic belt. The main elements of a geological structure of the Elikanskiy metamorphic core complex are the detachment zone, core and upper nappe. The detachment zone separating a core from the upper nappe is represented by a thick zone of blastomylonites and a zone of chlorite breccias. That zone was formed under the conditions of tangential stress and led to the exhumation and structural and metamorphic transformations of magmatic rocks of the Bukhtochinskiy Complex and metamorphic rocks of the Upper Olekma Complex, which compose the core of the considered structure. The upper nappe consists of Jurassic and Cretaceous stratified rocks of the Kyker–Akimin and Usuglinskiy basin and the Early Paleozoic–Mesozoic volcanoplutonic complexes in its southeastern framing. The Elikanskiy metamorphic core complex is a part of a huge belt of metamorphic core complexes which is traced along the northern border of the Mongolo-Okhotskiy orogenic belt on distance about 2000 km. The formation of the Elikanskiy metamorphic core complex as well as other similar complexes in the eastern part of the Central Asian orogenic belt is connected with collapse of the Late Mesozoic orogen which has resulted from the accretionary and collision events connected with closing of the Mongolo-Okhotskiy paleoocean basin and respectively formation of the Mongolo-Okhotskiy orogenic belt.