Tectonometamophic evolution of the Greater Himalayan sequence, Karnali valley, northwestern Nepal

dc.contributor.authorYakymchuk, Christopheren
dc.contributor.departmentGeological Sciences and Geological Engineeringen
dc.contributor.supervisorGodin, Laurenten
dc.date2010-09-20 09:23:07.103
dc.date.accessioned2010-09-21T19:26:23Z
dc.date.available2010-09-21T19:26:23Z
dc.date.issued2010-09-21T19:26:23Z
dc.degree.grantorQueen's University at Kingstonen
dc.descriptionThesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2010-09-20 09:23:07.103en
dc.description.abstractIn the Karnali valley of west Nepal, detailed mapping, thermobarometry, quartz-petrofabrics, vorticity analysis, and thermochronology delineate three tectonometamorphic domains separated by structural and metamorphic discontinuities. The lowest domain, the Lesser Himalayan sequence, is weakly metamorphosed and preserves evidence of primary sedimentary features and a polydeformational history. The Greater Himalayan sequence (GHS) is pervasively sheared and metamorphosed and overlies the Lesser Himalayan sequence along the Main Central thrust. The Greater Himalayan sequence is sub-divided into two tectonometamorphic domains that display contrasting metamorphic histories. The lower portion of the Greater Himalayan sequence contains garnet- to kyanite-grade rocks whose peak metamorphic assemblages developed during top-to-the-south directed shear and a metamorphic pressure gradient that increases up structural section. The upper portion of the Greater Himalayan sequence contains kyanite and sillimanite-grade migmatites that preserve polymetamorphic assemblages and a metamorphic pressure gradient that decreases up structural section. The upper and lower portions of the Greater Himalayan sequence are separated by a metamorphic discontinuity that roughly coincides with the bottom of the lowest migmatite unit. Vorticity estimates indicate roughly equal contributions of pure and simple shear during deformation of the upper and lower portions of the GHS. Quartz petrofabrics suggest deformation temperatures are equivalent to peak metamorphic temperatures in the lower Greater Himalayan sequence. These observations are consistent with channel flow tectonic models whereby the upper portion of the Greater Himalayan sequence is ductily extruded to the south while ductily accreting the subjacent lower portion of the Greater Himalayan sequence across a metamorphic discontinuity. 40Ar/39Ar thermochronology indicates Miocene homogeneous cooling of the Greater Himalayan sequence. Cooling rates of the GHS and the homogeneous cooling profile suggest east-west extensional exhumation followed peak-metamorphism and south-directed shearing and supports the hypothesis of the southeast propagation of the Gurla-Mandhata-Humla fault system into the Karnali valley.en
dc.description.degreeM.A.Sc.en
dc.identifier.urihttp://hdl.handle.net/1974/6058
dc.language.isoengen
dc.relation.ispartofseriesCanadian thesesen
dc.rightsThis publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.en
dc.subjectGreater Himalayan sequenceen
dc.subjectThermobarometryen
dc.subjectTectonicsen
dc.subjectHimalayaen
dc.subject40Ar/39Ar Thermochronologyen
dc.subjectMicrostructureen
dc.titleTectonometamophic evolution of the Greater Himalayan sequence, Karnali valley, northwestern Nepalen
dc.typethesisen
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