Kinematic analyses of orogen-parallel L-tectonites from Pelling-Munsiari thrust of Sikkim Himalayan fold thrust belt: Insights from multiple,incremental strain markers |
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| Institution: | 1. Department of Earth Sciences, Indian Institute of Science Education and Research Kolkata (IISERK), Mohanpur 741246, West Bengal, India;2. Department of Geology, Sonoma State University, 1801 E. Cotati Avenue, Rohnert Park, CA 94928, USA;1. Department of Earth Sciences and Environmental and Resources Engineering, Graduate School of Science and Engineering, Waseda University, Shinjuku, Tokyo 169-8050, Japan;2. Department of Earth Sciences, Faculty of Education and Integrated Arts and Sciences, Waseda University, Shinjuku, Tokyo 169-8050, Japan;1. Department of Earth System Sciences, Yonsei University, Seoul 03722, Republic of Korea;2. Geological Research Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 34132, Republic of Korea;3. Department of Geoenvironmental Sciences, Kongju National University, Gongju 32588, Republic of Korea;4. Division of Earth and Environmental Sciences, Korea Basic Science Institute, Chungbuk 28119, Republic of Korea;1. Istituto Nazionale di Geofisica e Vulcanologia, Pisa, Italy;2. Dipartimento di Scienze della Terra, University of Pisa, Italy;3. Dipartimento di Scienze Biologiche, Geologiche e Ambientali, University of Bologna, Italy;4. Geological Survey of Finland, Espoo, Finland;5. Currently at Rock Mechanic Consulting Finland Oy, Vantaa, Finland;1. Geology Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 34132, Republic of Korea;2. Department of Earth System Sciences, Yonsei University, Seoul 03722, Republic of Korea;3. School of Earth Sciences, The Ohio State University, Columbus, OH 43210, USA;4. School of Earth Sciences and Resources, China University of Geosciences, Beijing, 29 Xueyuan Road, Beijing 100083, China;5. Centre for Tectonics, Resources and Exploration, Department of Earth Sciences, University of Adelaide, SA 5005, Australia;6. Division of Earth and Environmental Science, Korea Basic Science Institute, Chungbuk 28119, Republic of Korea |
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| Abstract: | Fault rocks associated with the Pelling thrust (PT) in the Sikkim Himalayan fold thrust belt (FTB) change from SL tectonites to local, transport-parallel L-tectonites that are exposed in discontinuous klippen south of the PT zone. By estimating the incremental kinematic vorticity number (Wk) from quartz c-axes fabric, oblique fabric, and subgrains, we reconstruct a first-order, kinematic path of these L-tectonites. Quartz c-axes fabric suggests that the deformation initiated as pure-shear dominated (～56–96%) that progressively became simple-shear dominated (～29–54%), as recorded by the oblique fabric and subgrains in the L-tectonites. These rocks record a non-steady deformation where the kinematic vorticity varied spatially and temporally within the klippen.The L-tectonites record ～30% greater pure-shear than the PT fault rocks outside the klippen, and the greatest pure-shear dominated flow among the published vorticity data from major fault rocks of the Himalayan FTB. The relative decrease in the transport-parallel simple-shear component within the klippen, and associated relative increase of transport-perpendicular, pure-shear component, support the presence of a sub-PT lateral ramp in the Sikkim Himalayan FTB. This study demonstrates the influence of structural architecture for fault systems for controlling spatial and temporal variations of deformation fabrics and kinematic path of deforming thrust wedges. |
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| Keywords: | Sikkim Himalayan fold thrust belt Vorticity analysis Kinematic analysis Pelling-Munsiari thrust MCT L tectonites |
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