Diachronous deformation along the base of the Himalayan metamorphic core, west-central Nepal

Research Article| May 01, 2016 Diachronous deformation along the base of the Himalayan metamorphic core, west-central Nepal Rohanna Gibson; Rohanna Gibson 1Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario, K7L 3N6, Canada Search for other works by this author on: GSW Google Scholar Laurent Godin; Laurent Godin † 1Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario, K7L 3N6, Canada †Corresponding author: godinl@queensu.ca. Search for other works by this author on: GSW Google Scholar Dawn A. Kellett; Dawn A. Kellett 2Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, K1A 0E8, Canada Search for other works by this author on: GSW Google Scholar John M. Cottle; John M. Cottle 3Department of Earth Science, University of California, Santa Barbara, California 93106, USA Search for other works by this author on: GSW Google Scholar Douglas Archibald Douglas Archibald 1Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario, K7L 3N6, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information Rohanna Gibson 1Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario, K7L 3N6, Canada Laurent Godin † 1Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario, K7L 3N6, Canada Dawn A. Kellett 2Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, K1A 0E8, Canada John M. Cottle 3Department of Earth Science, University of California, Santa Barbara, California 93106, USA Douglas Archibald 1Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario, K7L 3N6, Canada †Corresponding author: godinl@queensu.ca. Publisher: Geological Society of America Received: 31 Mar 2015 Revision Received: 23 Nov 2015 Accepted: 05 Jan 2016 First Online: 09 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2016 Geological Society of America GSA Bulletin (2016) 128 (5-6): 860–878. https://doi.org/10.1130/B31328.1 Article history Received: 31 Mar 2015 Revision Received: 23 Nov 2015 Accepted: 05 Jan 2016 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Rohanna Gibson, Laurent Godin, Dawn A. Kellett, John M. Cottle, Douglas Archibald; Diachronous deformation along the base of the Himalayan metamorphic core, west-central Nepal. GSA Bulletin 2016;; 128 (5-6): 860–878. doi: https://doi.org/10.1130/B31328.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Geologic mapping combined with microstructural and geochronologic analyses from the lower Himalayan metamorphic core in west-central Nepal record along-strike similarity in flow style despite variability in the timing of metamorphism and deformation. The Main Central thrust zone at the base of the Himalayan metamorphic core varies in thickness, tectonostratigraphy, and metamorphic gradient along the 250 km of strike length studied. In situ U-Th/Pb geochronology of monazite sampled from an along-strike transect at the top of the high-strain zone records Eocene–Oligocene prograde metamorphism followed by Miocene retrograde metamorphism. The timing of prograde and retrograde metamorphism and the muscovite 40Ar/39Ar dates gradually decrease along strike from northwest to southeast. This age trend is punctuated by an abrupt ∼3–8 m.y. decrease in the age of prograde and retrograde metamorphism and muscovite 40Ar/39Ar dates near the Marsyandi River in central Nepal. Quartz crystallographic preferred orientation fabrics from a parallel transect along the base of the high-strain zone document similar flow style at ∼440 °C in central Nepal. Muscovite 40Ar/39Ar ages, interpreted to approximate the age of deformation at this structural level, decrease from ca. 7 to 4 Ma along strike from northwest to southeast. Diachronous deformation and metamorphism along strike in west-central Nepal demonstrate the necessity of incorporating more than a single transect into tectonic models. Along-strike tectonometamorphic variability in west-central Nepal spatially corresponds to faults in the Indian basement bounding the subsurface Faizabad ridge, highlighting the possible influence of inherited basement faults on the geometry of the basal Himalayan detachment, the Main Himalayan thrust, as well as the tectonic evolution of the structurally overlying Himalayan metamorphic core. This study highlights the potential influence of inherited structures on the overlying orogenic wedge and the probability of along-strike diachroneity of deformation in the Himalaya. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.