Delineation of lithosphere structure and characterization of the Moho geometry under the Himalaya–Karakoram–Tibet collision zone using surface-wave tomography
Published:September 25, 2019
Naresh Kumar, A. Aoudia, M. Guidarelli, Vivek G. Babu, Devajit Hazarika, D. K. Yadav, 2019. "Delineation of lithosphere structure and characterization of the Moho geometry under the Himalaya–Karakoram–Tibet collision zone using surface-wave tomography", Crustal Architecture and Evolution of the Himalaya–Karakoram–Tibet Orogen, Rajesh Sharma, Igor M. Villa, Santosh Kumar
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Group velocities for a period range of 6–60 s for the fundamental mode of the Rayleigh wave passing across the Himalaya–Karakoram–Tibet orogen are used to delineate the structure of the upper lithosphere using the data from 35 broadband seismic stations. 2D tomography velocity maps of group velocities were obtained at grids of 1° separation. Redefined local dispersion curves are inverted non-linearly to obtain 1D velocity models and to construct a 3D image of the S-wave structure down to a depth of 90 km.
The Moho discontinuity is correlated with c. 4.0 km s−1 S-wave velocity. The results depict a NE-dipping trend of the Moho depth from c. 40 km beneath the frontal part of the Himalaya to up to c. 70–80 km beneath the collision zone before shallowing substantially to c. 40 km beneath the Tarim Basin. The study also reveals thick deposits of sediments in the Indo-Gangetic plains and the Tarim Basin. A broad low-velocity zone at mid-crustal depth in the western Tibetan Plateau, the Karakoram region and the surface-collision part of the India–Eurasia tectonic plates is interpreted as the effect of partial melting and/or the presence of aqueous fluid. The high velocities in the southern deeper part indicate that the lower crust and uppermost mantle of the Indian Plate are dense and cold.
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Crustal Architecture and Evolution of the Himalaya–Karakoram–Tibet Orogen
CONTAINS OPEN ACCESS
This volume comprises 17 contributions that address the architecture and geodynamic evolution of the Himalaya–Karakoram–Tibet (HKT) system, covering wide aspects, from the active seismicity of the present day to the remnants of the Proterozoic orogen. The articles investigate the HKT system at different scales, blending field research with laboratory studies. The role of various lithospheric components and their inheritance in the geodynamic and magmatic evolution of the HKT system through time, and their links to global geological events, are studied in the field. The laboratory research focuses on the (sub-)micrometre scale, detailing micro-structural geology, crystal chemistry, geochronology, and the study of circulating fluids, their preservation (trapped in fluid inclusions) and their evolution, distribution, migration and interaction with the solid host. An orogen over 2000 km long can be understood only if the processes at the nanometre and micrometre scales are taken into account. The contributions in this volume successfully combine these scales to enhance our understanding of the HKT system.