Tectonics and geodynamics of Gorny Altai and adjacent structures of the Altai–Sayan folded area

Abstract

Packages of Late Paleozoic tectonic nappes and associated major NE-trending strike-slip faults are widely developed in the Altai–Sayan folded area. Fragments of early deformational phases are preserved within the Late Paleozoic allochthons and autochthons. Caledonian fold-nappe and strike-slip structures, as well as accompanying metamorphism and granitization in the region, are typical of the EW-trending suture-shear zone separating the composite Kazakhstan–Baikal continent and Siberia. In the Gorny Altai region, the Late Paleozoic nappes envelop the autochthon, which contains a fragment of the Vendian–Cambrian Kuznetsk–Altai island arc with accretionary wedges of the Biya–Katun’ and Kurai zones. The fold-nappe deformations within the latter zones occurred during the Late Cambrian (Salairian) and can thus be considered Salairian orogenic phases. The Salairian fold-nappe structure is stratigraphically overlain by a thick (up to 15 km) well-stratified rock unit of the Anyui–Chuya zone, which is composed of Middle Cambrian–Early Ordovician fore-arc basin rocks unconformably overlain by Ordovician–Early Devonian carbonate-terrigenous passive-margin sequences. These rocks are crosscut by intrusions and overlain by a volcanosedimentary unit of the Devonian active margin. The top of the section is marked by Famennian–Visean molasse deposits onlapping onto Devonian rocks. The molasse deposits accumulated above a major unconformity reflects a major Late Paleozoic phase of folding, which is most pronounced in deformations at the edges of the autochthon, nearby the Kaim, Charysh–Terekta, and Teletskoe–Kurai fault nappe zones. Upper Carboniferous coal-bearing molasse deposits are preserved as tectonic wedges within the Charysh–Terekta and Teletskoe–Kurai fault nappe zones. Detrital zircon ages from Middle Cambrian–Early Ordovician rocks of the Anyui–Chuya fore-arc zone indicate that they were primarily derived from Upper Neoproterozoic–Cambrian igneous rocks of the Kuznetsk–Altai island arc or, to a lesser extent, from an Ordovician–Early Devonian passive margin. A minor age population is represented by Paleoproterozoic grains, which was probably sourced from the Siberian craton. Zircons from the Late Carboniferous molasse deposits have much wider age spectra, ranging from Middle Devonian–Early Carboniferous to Late Ordovician–Early Silurian, Cambrian–Early Ordovician, Mesoproterozoic, Early–Middle Proterozoic, and early Paleoproterozoic. These ages are consistent with the ages of igneous and metamorphic rocks of the composite Kazakhstan–Baikal continent, which includes the Tuva-Mongolian island arc with accreted Gondwanan blocks, and a Caledonian suture-shear zone in the north. Our results suggest that the Altai–Sayan region is represented by a complex aggregate of units of different geodynamic affinity. On the one hand, these are continental margin rocks of western Siberia, containing only remnants of oceanic crust embedded in accretionary structures. On the other hand, they are represented by the Kazakhstan–Baikal continent composed of fragments of Gondwanan continental blocks. In the Early–Middle Paleozoic, they were separated by the Ob’–Zaisan oceanic basin, whose fragments are preserved in the Caledonian suture-shear zone. The movements during the Late Paleozoic occurred along older, reactivated structures and produced the large intracontinental Central Asian orogen, which is interpreted to be a far-field effect of the colliding East European, Siberian, and Kazakhstan–Baikal continents.

Late-Paleozoic emplacement and Meso-Cenozoic reactivation of the southern Kazakhstan granitoid basement

“…3b-c), resulting in the gradual consumption of surrounding oceanic lithosphere and final amalgamation of the ancestral CAOB by the late Permian (e.g. Buslov et al, 2004Buslov et al, , 2013Windley et al, 2007). More details about the geodynamic evolution of paleo-Kazakhstan during the Paleozoic can be found in e.g.…”

Tectonics and Geodynamics of the Altai-Junggar Orogen in the Vendian-Paleozoic: Implications for the Continental Evolution and Growth of the Central Asian Fold Belt

“…The recent results from detailed geological mapping, structural analysis and geochronological studies [Buslov et al, 2001[Buslov et al, , 2003Korobkin, Buslov, 2011;Smirnova et al, 2002;Cai et al, 2011aCai et al, , 2011bCai et al, , 2011cCai et al, , 2014Chen et al, 2015] were used to identify the following tectonic elements of the Central Asian fold belt [Buslov, 2011;Dobretsov, Buslov, 2007, 2011Buslov et al, 2013] (Fig. 1):…”

Late Paleozoic low-angle southward-dipping thrust in the Züünharaa area, Mongolia: tectonic implications for the geological structures in the Sayan-Baikal and Hangai-Daur belts

“…1b), make it clear that the Late Paleozoic low-angle southward-dipping thrust can generally be recognized in both the HD and SB belts. It should be noted that Proterozoic-Early Paleozoic sedimentary rocks are intruded by Cambrian-Ordovician granitic rocks and unconformably overlain by Late Paleozoic sedimentary rocks in the SB belt (e.g., Parfenov et al 2009;Buslov et al 2013). In the Haraa terrane of the HD belt, however, Cambrian-Lower Ordovician sedimentary rocks are intruded by Cambrian-Silurian granitic rocks and are unconformably overlain by Devonian-Carboniferous volcaniclastic and clastic rocks (e.g., Tomurtogoo et al 1998;Tomurtogoo 2012).…”