Did the Paleo-Asian Ocean between North China Block and Mongolia Block exist during the Late Paleozoic? First paleomagnetic evidence from central-eastern Inner Mongolia, China

Abstract : The tectonic evolution of the Paleo-Asian Ocean between the North China Block (NCB) and the Mongolia Block (MOB) is a contentious issue, and geodynamic models remain speculative. In an effort to puzzle out this controversy, a paleomagnetic study was carried out on the Silurian to Permian formations in central- eastern Inner Mongolia (China). More than 680 sedimentary and volcanic samples were collected from 86 sites. We have established titanium-poor magnetite and hematite as the principal magnetic carriers. AMS measurements demonstrate negligible deformation of the majority of study rocks with sedimentary fabrics. From primary magnetizations, a Late Devonian and a Permian pole are calculated for IMB at: λ = 46.8°N, φ = 349.1°E, dp = 14.6°, dm = 27.3° with N = 3 and λ = 48.7°N, φ = 3.7°E, dp = 5.2°, dm = 9.1° with N = 6, respectively. Two stages of secondary magnetization are also identified probably due to Early Permian and Early Cretaceous magmatic events. As preliminary results, the comparison of our new paleomagnetic poles with available data from NCB, MOB and Siberia indicates that (1) the paleolatitude of IMB, NCB and MOB are consistent between Late Devonian and Permian, suggesting pre-Late Devonian closure of the Paleo-Asian Ocean and further evaluation of these three blocks as a single entity; (2) post-Permian intracontinental deformation was significant and characterized by block rotations, which are due to strike-slip faulting within the welded NCB-IMB-MOB block.
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Pan Zhao, Yan Chen, Bei Xu, Michel Faure, Guanzhong Shi, et al.. Did the Paleo-Asian Ocean between North China Block and Mongolia Block exist during the Late Paleozoic? First paleomagnetic evidence from central-eastern Inner Mongolia, China. Journal of Geophysical Research : Solid Earth, American Geophysical Union, 2013, 118, pp.1873-1894. ⟨10.1002/jgrb.50198⟩. ⟨insu-00819742⟩

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