Abstract
Abstract —The Kolyvan’–Tomsk folded zone (KTFZ) is a late Permian collisional orogen in the northwestern section of the Central Asian Orogenic Belt. The Mesozoic history of the KTFZ area includes Late Triassic–Early Jurassic and Late Jurassic–Early Cretaceous orogenic events. The earlier event produced narrow deep half-ramp basins filled with Early–Middle Jurassic molasse south of the KTFZ, and the later activity rejuvenated the Tomsk thrust fault, whereby the KTFZ Paleozoic rocks were thrust over the Early–Middle Jurassic basin sediments. The Mesozoic orogenic events induced erosion and the ensuing exposure of granitoids (Barlak complex) that were emplaced in a within-plate context after the Permian collisional orogeny. Both events were most likely associated with ocean closure, i.e., the Paleothetys Ocean in the Late Triassic–Early Jurassic and the Mongol–Okhotsk Ocean in the Late Jurassic–Early Cretaceous. The apatite fission track (AFT) ages of granitoids from the Ob’ complex in the KTFZ range between ~120 and 100 Ma (the Aptian and the Albian). The rocks with Early Cretaceous AFT ages were exhumed as a result of denudation and peneplanation of the Early Cretaceous orogeny, which produced a vast Late Cretaceous–Paleogene planation surface. The tectonic pattern of the two orogenic events, although being different in details, generally inherited the late Paleozoic primary collisional structure of the Kolyvan’–Tomsk zone.
Highlights
The Kolyvan’–Tomsk Folded Zone (KTFZ) was interpreted as an exposed northern flank of the Ob’–Zaisan folded system within the Central Asian Orogenic Belt (Matveevskaya, 1969) or as a northwestern margin of the Altai–Sayan Folded Area (Sotnikov et al, 1999)
We review the available geological data on continental orogeny in the KFTZ and first thermal history models based on apatite fission track (AFT) thermochronology for late Permian granitoids
The Mesozoic orogenic processes led to erosional exposure of the Kolyvan’–Tomsk folded zone (KTFZ) late Permian and Triassic granitoids of the KTFZ
Summary
The Kolyvan’–Tomsk Folded Zone (KTFZ) was interpreted as an exposed northern flank of the Ob’–Zaisan folded system within the Central Asian Orogenic Belt (Matveevskaya, 1969) or as a northwestern margin of the Altai–Sayan Folded Area (Sotnikov et al, 1999). The folded zone is a late Paleozoic fold-and-thrust belt, ~450 km long and 60–100 km wide, striking in northeastern direction (Fig. 1). It is buried under Mesozoic–Cenozoic sediments of the West Siberian Basin in the south, west, and north and is thrust over the early Paleozoic Salair complexes and the late Paleozoic Kuznetsk basin in the southeast. The neotectonic mountain building is considered a farfield effect of the Eocene India–Eurasia collision (Molnar and Tapponnier, 1975; Hendrix et al, 1994; Dobretsov et al, 1996; Yin and Harrison, 2000; De Grave et al, 2007a; Delvaux et al, 2013), and the ancient orogenic events can be
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