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Control of detachment geometry on lateral variations in exhumation rates in the Himalaya: Insights from low-temperature thermochronology and numerical modeling

Abstract : The Himalayan range is commonly presented as largely laterally uniform from west to east. However, geological structures, topography, precipitation rate, convergence rates, and low-temperature thermochronological ages all vary significantly along strike. Here, we focus on the interpretation of thermochronological data sets in terms of along-strike variations in geometry and kinematics of the main crustal detachment underlying the Himalaya: the Main Himalayan Thrust (MHT). We report new apatite fission track (AFT) ages collected along north-south transects in western and eastern central Nepal (at the latitudes of the Annapurna and Langtang massifs, respectively). AFT ages are consistently young (<3 Ma) along both N-S transects in the high-relief zone of the Higher Himalaya and increase (4 to 6 Ma) toward the south in the Lesser Himalaya. We compare our new data to published low-temperature thermochronological data sets for Nepal and the Bhutan Himalaya. We use the full data set to perform both forward and inverse thermal kinematic modeling with a modified version of the Pecube code in order to constrain potential along-strike variations in the kinematics of the Himalayan range. Our results show that lateral variations in the geometry of the MHT (in particular the presence or absence of a major crustal-scale ramp) strongly control the kinematics and exhumation history of the orogen.
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https://hal-insu.archives-ouvertes.fr/insu-00681449
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Submitted on : Wednesday, March 21, 2012 - 3:20:25 PM
Last modification on : Friday, July 17, 2020 - 5:09:03 PM

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Xavier Robert, Peter van der Beek, Jean Braun, Claire Perry, Jean-Louis Mugnier. Control of detachment geometry on lateral variations in exhumation rates in the Himalaya: Insights from low-temperature thermochronology and numerical modeling. Journal of Geophysical Research : Solid Earth, American Geophysical Union, 2011, 116, pp.B05202. ⟨10.1029/2010JB007893⟩. ⟨insu-00681449⟩

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