Permian magmatism and lithospheric deformation in the Altai caused by crustal and mantle thermal processes

Abstract

New structural and petrological data have been obtained for the zone of Siberia-Kazakhstan oblique collision for Permian time. In terms of classical tectonics, the area coincides with the Zaisan folded area produced by closure of the Char paleo-ocean in the Late Carboniferous. However, the extent, structure, and composition of magmatism at the Carboniferous-Permian (280±10 Ma) and Permian-Triassic (250±5 Ma) boundaries require an active control from Morgan-type lower mantle plumes (Tarim and Siberian plumes). Structure formation in the lithosphere and heat sources of magmatism have been simulated in a 3D model including lithospheric strain rates (with regard to viscosity layering) and subcontinental upper mantle convection. According to our model, heat supply from slab break-off and/or delamination of lithosphere is insufficient to maintain large-scale mantle-crustal magmatism in the case of oblique collision between 80–100 km thick plates (“soft collision”). The Late Paleozoic-Early Mesozoic Altai is considered as a model of a large hot shear zone, a particular structure produced by interference of plate- and plume-tectonic processes. Special attention is given to structural and petrological markers of plume tectonics (reported for the case of the Altai collisional shear system), with their diagnostic features useful for understanding geodynamics of other similar regions.

Intracontinental strike-slip faults, associated magmatism, mineral systems and mantle dynamics: examples from NW China and Altay-Sayan (Siberia)

“…Biotite from a tonalitic gneiss records an age of 270 ± 8 Ma. Other Ar-Ar age data from the Irtysh fault system (Vladimirov et al, 2008) are: 281 ± 2.4, 277 ± 7, 283 ± 7, 283 ± 1.6, 282 ± 1.5, 269 ± 2.3 and 264 ± 3 Ma. These age data record two events: a left-lateral ductile 285-270 Ma and a brittle-ductile 270-260 Ma (Briggs et al, 2007;Vladimirov et al, 2008).…”

Tectonic history of the Irtysh shear zone (NE Kazakhstan): New constraints from zircon U/Pb dating, apatite fission track dating and palaeostress analysis

“…Note that geographical North is at an angle relative to the figure's top. Intrusive complexes are indicated and colour-coded with respect to their inferred emplacement age (based on Vladimirov et al (2008), Wang et al (2009) andChen et al (2010)). Sample locations for this study are shown by yellow stars on the map.…”

“…Multi-mineral 40 Ar/ 39 Ar ages record two major stages of left-lateral deformation in the ISZ at $285-270 Ma and $270-260 Ma (Travin et al, 2001). It is thought that both the ISZ and CSZ accommodated more than 1000 km sinistral strike-slip displacement during this period of time (Melnikov et al, 1997;Burtman et al, 1998;Buslov et al, 2004;Vladimirov et al, 2008). The Rudny-Altai granitoids (NE of the ISZ) mainly have Devonian -Early Carboniferous crystallization ages (Fig.…”

“…Buslov et al, 2001;Windley et al, 2007). The Hercynian (late Early Carboniferous) closure of this basin provoked the final amalgamation of the ancestral CAOB (S ßengör et al, 1993;Chikov and Zinoviev, 1996;Buslov et al, 2001Buslov et al, , 2004Vladimirov et al, 2003Vladimirov et al, , 2008Khromykh et al, 2011). This collision occurred along the Char ophiolitic suture-shear zone (CSZ) (Fig.…”

“…2). Hence, the Kalba-Narym intrusions are thought to be emplaced in a post-collisional setting associated with ISZ activity (Vladimirov et al, , 2008. The granitoids associated with the ISZ are deformed and show a ductile mylonitic fabric, indicating that the ISZ remained active after their emplacement (Chikov and Zinoviev, 1996;Melnikov et al, 1997;Buslov et al, 2004;Pirajno, 2010).…”