Manifestations of the Late Carboniferous and Early Permian stages of formation of nappe-fold structures in the southern framework of the Siberian platform (East Sayany, South Siberia)

Abstract

The geological structure of the Tunka Goltsy (the Tunka Range) of the East Sayany is characterized by a complex nappefold structure, composed mainly of Paleozoic terrigenous and carbonate rocks and their metamorphosed analogues (1-3). It is generally rec� ognized that the nappefold structure of the East Sa� yany, including its southeastern segment, regarded as the Tunka terrain (3) or Ilchirskaya zone (4), formed in the Ordovician as a result of collision between the Tuva-Mongolian microcontinent and the Siberian continent. As referred to in (5), the Ordovician-Mid� dle Paleozoic deformations over the entire vast terri� tory of Central Asia, from the Olkhon zone of the Pribaikalie to the North Kazakhstan, were manifested as a result of the closing of the oceanic basin and the subsequent collision between the Kazakhstan- Baikalian complex continent (including the Tuva- Mongolian microcontinent) and the Siberian conti� nent. In the Ordovician the Olkhon nappeoverthrust zone was formed along the southeastern framework of the Siberian Craton. In addition, the metamorphism was manifested over the entire vast territory of the East Sayany that could probably be connected with nappe formation. In the Late Ordovician-Silurian, the oblique slipthrust structures, magmatism, and meta� morphism were manifested in the Sangilen highlands and Tuva. Later, the deformations continued. In the Late Devonian-Early Carboniferous, the dextral strikeslip fault Charysh-Terektinskaya zone was formed; in the Late Carboniferous, the Kurayskaya and Kuznetsko-Teletsko-Bashkaus sinistral strike� slip shear zones were formed. In the Late Carboniferous-Permian, the collision between the East European, Kazakhstan-Baikalian, and Siberian continents took place (5, 6). In East Kazakhstan, the sinistral strikeslip movements took place in the band of more than 400 km width along the Chara ophiolite zone and the Irtysh and Northeastern shear zones. The age of deformation rejuvenates regu� larly to the east towards the internal part of the Sibe� rian continent; the movement amplitude along shears decreases in the same direction from several thousand to a hundred kilometers. In the late Palaeozoic in the Tunka Goltsy and the adjacent regions, a number of geological events of Late Carboniferous and Early Permian age are distin�