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Fault weakeningacross thefrictional‐viscoustransition zone,Karakoram Fault Zone,NW Himalaya David WallisR. J. PhillipsGeoffrey E. Lloyd2013 год

Fault weakening across the frictional‐viscous transition zone, Karakoram Fault Zone, NW Himalaya
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Аннотация: Abstract Exhumed fault rocks formed in the frictional‐viscous transition zone (FVTZ) provide test material that can be used to assess the strength of natural fault zones. In the Karakoram Fault Zone (KFZ), such rocks contain evidence of several long‐term weakening mechanisms associated with reduced coefficients of friction (<0.4). The Nubra, Tangtse, and Arganglas strands of the KFZ are focused along metavolcano‐sedimentary formations indicating weakness relative to the bounding granitoids. Synkinematic retrogression suggests that reaction softening has weakened the margins of granitoids along the Nubra and Tangtse strands and the Nubra Formation within the Nubra strand. The resultant phyllosilicates have formed well‐developed interconnected weak layers within phyllonites and granitic mylonites. Micaceous foliae with increased proportions of opaque minerals in granitic mylonites suggest that fluid‐assisted diffusive mass transfer aided deformation within the Nubra and Tangtse strands. Microstructures within Nubra strand phyllonites suggest that frictional‐viscous flow accommodated deformation at low shear stresses in the FVTZ. Multiple generations of veining within each strand indicate overpressured pore fluids within the fault zone across a range of depths. Active springs and travertines along the fault indicate ongoing suprahydrostatic fluid flow within the KFZ. Despite such evidence for weakening mechanisms, the KFZ is currently locked and most likely generates moment magnitude 7.5+ earthquakes. Evidence for multiple fault weakening mechanisms reduces potential for shear heating within the KFZ and suggests that the long‐term strength of the lithosphere must reside below the depth of penetration of the fault.
Год издания: 2013
Авторы: David Wallis, R. J. Phillips, Geoffrey E. Lloyd
Издательство: Wiley
Источник: Tectonics
Ключевые слова: earthquake and tectonic studies, High-pressure geophysics and materials, Geological and Geochemical Analysis
Другие ссылки: Tectonics (PDF)
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White Rose Research Online (University of Leeds) (HTML)
Oxford University Research Archive (ORA) (University of Oxford) (PDF)
Oxford University Research Archive (ORA) (University of Oxford) (HTML)