Structural evolution of the Irtysh Shear Zone (northwestern China) and implications for the amalgamation of arc systems in the Central Asian Orogenic Belt

Li, Pengfei, Sun, Min, Rosenbaum, Gideon, Cai, Keda and Yu, Yang (2015) Structural evolution of the Irtysh Shear Zone (northwestern China) and implications for the amalgamation of arc systems in the Central Asian Orogenic Belt. Journal of Structural Geology, 80 142-156. doi:10.1016/j.jsg.2015.08.008

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Author Li, Pengfei
Sun, Min
Rosenbaum, Gideon
Cai, Keda
Yu, Yang
Title Structural evolution of the Irtysh Shear Zone (northwestern China) and implications for the amalgamation of arc systems in the Central Asian Orogenic Belt
Journal name Journal of Structural Geology   Check publisher's open access policy
ISSN 1873-1201
0191-8141
Publication date 2015-11-01
Sub-type Article (original research)
DOI 10.1016/j.jsg.2015.08.008
Open Access Status File (Author Post-print)
Volume 80
Start page 142
End page 156
Total pages 15
Place of publication Kidlington, Oxford, United Kingdom
Publisher Pergamon Press
Language eng
Formatted abstract
The NW-SE Irtysh Shear Zone is a major tectonic boundary in the Central Asian Orogenic Belt (CAOB), which supposedly records the amalgamation history between the peri-Siberian orogenic system and the Kazakhstan/south Mongolia orogenic system. However, the tectonic evolution of the Irtysh Shear Zone is not fully understood. Here we present new structural and geochronological data, which together with other constraints on the timing of deformation suggests that the Irtysh Shear Zone was subjected to three phases of deformation in the late Paleozoic. D1 is locally recognized as folded foliations in low strain areas and as an internal fabric within garnet porphyroblasts. D2 is represented by a shallowly dipping fabric and related ~ NW-SE stretching lineations oriented sub-parallel to the strike of the orogen. D2 foliations are folded by ~ NW-SE folds (F3) that are bounded by a series of mylonite zones with evidence for sinistral/reverse kinematics. These fold and shear structures are kinematically compatible, and thus interpreted to result from a transpressional deformation phase (D3). Two samples of mica schists yielded youngest detrital zircon peaks at ~322 Ma, placing a maximum constraint on the timing of D1-D3 deformation. A ~ NE-SW granitic dyke swarm (~252 Ma) crosscuts D3 fold structures and mylonitic fabrics in the central part of the shear zone, but is displaced by a mylonite zone that represents the southern boundary of the Irtysh Shear Zone. This observation indicates that the major phase of D3 transpressional deformation took place prior to ~252 Ma, although later phases of reactivation in the Mesozoic and Cenozoic are likely. The late Paleozoic deformation (D1-D3 at ~322-252 Ma) overlaps in time with the collision between the Chinese Altai and the intra-oceanic arc system of the East Junggar. We therefore interpret that three episodes of late Paleozoic deformation represent orogenic thickening (D1), collapse (D2), and transpressional deformation (D3) during the convergence between the Chinese Altai and the East Junggar. On a larger scale, late Paleozoic sinistral shearing (D3), together with dextral shearing farther south, accommodated the eastward migration of internal segments of the western CAOB, possibly associated with the amalgamation of multiple arc systems and continental blocks during the late Paleozoic.
Keyword Accretionary orogen
Central Asian Orogenic Belt
Chinese Altai
Irtysh Shear Zone
Junggar
Structural synthesis
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Earth Sciences Publications
Official 2016 Collection
 
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Citation counts: TR Web of Science Citation Count  Cited 9 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 10 times in Scopus Article | Citations
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Created: Tue, 08 Sep 2015, 03:34:42 EST by Dr Gideon Rosenbaum on behalf of School of Earth Sciences