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New paleomagnetic results of upper Permian - lower Triassic volcanic sequences from the Hoa Binh area, northwest Vietnam

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This result implies that insignificant cumulative displacement has occurred along the Ailao Shan/Red River fault system during the Cenozoic India-Eurasia collision. | Vietnam Journal of Earth Sciences 36 (2014) 413-423 Vietnam Academy of Science and Technology Vietnam Journal of Earth Sciences (VAST) Website: http://www.vjs.ac.vn/index.php/jse New paleomagnetic results of upper Permian - lower Triassic volcanic sequences from the Hoa Binh area, northwest Vietnam Cung Thuong Chi1, John W. Geissman2, Hoang Van Quy1, Nguyen Thi Phuong Dung1, Nguyen Thi Hoc1 1 Institute of Geological Sciences, Vietnam Academy of Science and Technology Department of Geosciences, University of Texas at Dallas, ROC 21, 800 West Campbell Road, Richardson, Texas 75080-3021, USA 2 Accepted 25 December 2014 ABSTRACT Oriented-core samples (125) from twelve sites collected from the Late Permian-Early Triassic volcanic Vien Nam formation exposed at the Hoa Binh Dam area, northwest Vietnam yield interpretable magnetizations in progressive demagnetization. The characteristic remanent magnetization (ChRM) components carried by magnetite and hematite are successfully isolated from secondary components and reveal a mean, in situ (geographic coordinates) paleomagnetic direction of Decl. = 33.8 o, Incl. = -28.4o ( 95 = 9.5o, k = 30.3, N = 9 site mean directions), corresponding to a virtual geomagnetic pole located at = 41.1 oN, = 239.8 oE and a paleo-latitude for the study area situated at ~15 oS during the Late Permian to Early Triassic. A comparison of the pole we report in this study with the Late Permian-Early Triassic part of the South China Block apparent polar wander path shows that this volcanic terrane of northwest Vietnam has been close to if not a coherent part of the South China Block since the Late Permian. This result implies that insignificant cumulative displacement has occurred along the Ailao Shan/Red River fault system during the Cenozoic India-Eurasia collision. © 2014 Vietnam Academy of Science and Technology 1. Introduction Southeast Asia consists of a complex assemblage of Gondwana-derived continental blocks that were rifted from .