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Neogene-Recent Reactivation of Pre-Existing Faults in South-Central Vietnam, with Implications for the Extrusion of Indochina
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  • Nicholas Philip Richard,
  • Caroline M Burberry,
  • Nguyen Hoang,
  • Le Duc Anh,
  • Sang Q Dinh,
  • Lynne J Elkins
Nicholas Philip Richard
University of Nebraska-Lincoln

Corresponding Author:[email protected]

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Caroline M Burberry
University of Nebraska
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Nguyen Hoang
Institute of Geological Sciences, VAST
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Le Duc Anh
Vietnam Institute of Science and Technology
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Sang Q Dinh
South Vietnam Geological Mapping Division
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Lynne J Elkins
University of Nebraska-Lincoln
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Vietnam contains a complex series of faults coupled with a diffuse igneous province that has been active since the mid-Miocene. However, existing fault maps demonstrate little consensus over the location of Neogene basalt flows and relative ages of mapped faults, which complicates interpretations of tectonic model for the evolution of Indochina. This paper identifies discrete tectonic blocks within Vietnam and aims to define the Neogene-Recent tectonic setting and kinematics of south-central Vietnam by analyzing the orientation, kinematics, and relative ages of faults across each block. Fault ages and relative timing are constrained using cross-cutting relationships with dated basalt flows and between slickenside sets. Remote sensing results show distinct fault trends within individual blocks that are locally related to the orientations of the basement-involved block-bounding faults. Faults observed in the field indicate an early phase of dip-slip motion and a later phase of strike-slip motion, recording the rotation of blocks within a stress field. Faulting after the change in motion of the Red River Fault Zone is inferred, as faults cross-cut basalt flows as young as ~0.6 Ma. Strike-slip motion on block-bounding faults is consistent with rotation and continuous extrusion of each block within south-central Vietnam. The rotation of the blocks is attributed to the “continuum rubble” behavior of small crustal blocks influenced by extrusion-driven asthenospheric flow after the collision between India and Eurasia. We deduce a robust lithospheric-asthenospheric coupling in the extrusion model, which holds implications for other regions experiencing extrusion even in the absence of a free surface.
21 Dec 2023Submitted to ESS Open Archive
27 Dec 2023Published in ESS Open Archive