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Late Oligocene high-temperature shear zones in the core of the higher Himalayan Crystallines (Lower Dolpo, western Nepal)

Carosi, R; Montomoli, C; Rubatto, Daniela; Visona, Dario

Description

A high-temperature shear zone, Toijem shear zone, with a top-to-the-SW sense of shear affects the core of the Higher Himalayan Crystallines (HHC) in western Nepal. The shear zone developed during the decompression, in the sillimanite stability field, of rocks that previously underwent relatively high-pressure metamorphism deformed under the kyanite stability field. PT conditions indicate that the footwall experienced higher pressure (∼9 kbar) than the hanging wall (∼7 kbar) and similar...[Show more]

dc.contributor.authorCarosi, R
dc.contributor.authorMontomoli, C
dc.contributor.authorRubatto, Daniela
dc.contributor.authorVisona, Dario
dc.date.accessioned2015-12-07T22:23:22Z
dc.identifier.issn0278-7407
dc.identifier.urihttp://hdl.handle.net/1885/20644
dc.description.abstractA high-temperature shear zone, Toijem shear zone, with a top-to-the-SW sense of shear affects the core of the Higher Himalayan Crystallines (HHC) in western Nepal. The shear zone developed during the decompression, in the sillimanite stability field, of rocks that previously underwent relatively high-pressure metamorphism deformed under the kyanite stability field. PT conditions indicate that the footwall experienced higher pressure (∼9 kbar) than the hanging wall (∼7 kbar) and similar temperatures (675°-700°C). Monazite growth constrains the initial activity of the shear zone at 25.8 ± 0.3 Ma, before the onset of the Main Central Thrust zone, whereas the late intrusion of a crosscutting granitic dike at 17 ± 0.2 Ma limits its final activity. Monazites in kyanite-bearing gneisses from the footwall record prograde metamorphism in the HHC from ∼43 to 33 Ma. The new data confirm that exhumation of the HHC started earlier in western Nepal than in other portions of the belt and before the activity of both the South Tibetan Detachment System (STDS) and Main Central Thrust (MCT) zones. As a consequence, western Nepal represents a key area where the channel-flow-driven mechanism of exhumation, supposed to be active from Bhutan to central-eastern Nepal, does terminate. In this area, exhumation of crystalline units occurred by foreland propagation of ductile and, subsequently, brittle deformation.
dc.publisherAmerican Geophysical Union
dc.sourceTectonics
dc.subjectKeywords: Brittle deformation; High temperature; Initial activity; Late Oligocene; Main central thrusts; Shear zone; Tibetans; Hydraulic structures; Kyanite deposits; Monazite; Phosphate minerals; Silicate minerals; Crystalline materials; brittle deformation; core
dc.titleLate Oligocene high-temperature shear zones in the core of the higher Himalayan Crystallines (Lower Dolpo, western Nepal)
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume29
dc.date.issued2010
local.identifier.absfor040303 - Geochronology
local.identifier.absfor040312 - Structural Geology
local.identifier.absfor040313 - Tectonics
local.identifier.ariespublicationu4598381xPUB13
local.type.statusPublished Version
local.contributor.affiliationCarosi, R, Universita di Pisa
local.contributor.affiliationMontomoli, C, Universita di Pisa
local.contributor.affiliationRubatto, Daniela, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationVisona, Dario, University of Padova
local.description.embargo2037-12-31
local.bibliographicCitation.issueTC4029
local.bibliographicCitation.startpage1
local.bibliographicCitation.lastpage20
local.identifier.doi10.1029/2008TC002400
local.identifier.absseo970104 - Expanding Knowledge in the Earth Sciences
dc.date.updated2016-02-24T11:11:54Z
local.identifier.scopusID2-s2.0-77956286882
local.identifier.thomsonID000281418500001
CollectionsANU Research Publications

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