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A structural analysis of the Main Central Thrust zone, Langtang National Park, central Nepal Himalaya

1992; Geological Society of America; Volume: 104; Issue: 11 Linguagem: Inglês

10.1130/0016-7606(1992)104 2.3.co;2

1943-2674

Allison Macfarlane, K. V. Hodges, Daniel R. Lux,

Landslides and related hazards

Research Article| November 01, 1992 A structural analysis of the Main Central Thrust zone, Langtang National Park, central Nepal Himalaya A. M. MACFARLANE; A. M. MACFARLANE 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 Search for other works by this author on: GSW Google Scholar K. V. HODGES; K. V. HODGES 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 Search for other works by this author on: GSW Google Scholar D. LUX D. LUX 2Department of Geological Sciences, University of Maine at Orono, Orono, Maine 04469 Search for other works by this author on: GSW Google Scholar Author and Article Information A. M. MACFARLANE 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 K. V. HODGES 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 D. LUX 2Department of Geological Sciences, University of Maine at Orono, Orono, Maine 04469 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1992) 104 (11): 1389–1402. https://doi.org/10.1130/0016-7606(1992)104 2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation A. M. MACFARLANE, K. V. HODGES, D. LUX; A structural analysis of the Main Central Thrust zone, Langtang National Park, central Nepal Himalaya. GSA Bulletin 1992;; 104 (11): 1389–1402. doi: https://doi.org/10.1130/0016-7606(1992)104 2.3.CO;2 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 The Main Central Thrust (MCT) is one of the most tectonically significant structures in the Himalayan orogen. Detailed geologic mapping and structural analysis of the MCT in the Langtang National Park region of central Nepal reveals that this segment of the fault zone experienced multiple episodes of south-directed movement, under both brittle and ductile conditions, during the Tertiary period. Early (mid-Miocene) movement resulted in the development of mylonitic fabrics synchronous with amphibolite-facies metamorphism. The mean orientation of the dominant mylonitic foliation is N28°W, 38°NE. An associated mineral/stretching lineation plunges 40° to N40°E. Kinematic indicators suggest hanging-wall movement to the southwest relative to the footwall along the north-dipping fault. It is not possible to constrain the magnitude of high-temperature displacement on the MCT at the longitude of Langtang. Late-stage structures in the MCT zone at Langtang include a series of imbricate, brittle thrust faults that separate different lithostratigraphic units and correspond to metamorphic discontinuities. We interpret this fault system as a duplex structure. Muscovite 40Ar/39Ar cooling ages from the MCT zone range from 8.9-6.9 Ma. Because the nominal closure temperature of Ar diffusion in muscovite (approximately 625 K) is higher than the apparent temperature conditions under which late brittle deformation occurred, we suggest that brittle deformation was a latest Miocene-Pliocene phenomenon. Another major Himalayan fault, the Main Boundary Thrust (MBT), was developing to the south of Langtang at approximately the same time. We speculate that brittle faulting within the MCT zone may have initiated as the MCT zone was transported over a ramp in the MBT. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.