Twenty million years of continuous deformation along the Karakorum fault, western Tibet:
A thermochronological analysis
Franck Valli 1, Nicolas Arnaud 2, Philippe Hervé Leloup 3, Edward R. Sobel 4, Gweltaz Mahéo 3, Robin Lacassin 1, Stéphane Guillot 5, Haibing Li 1 & 6, Paul Tapponnier 1,
and Zhiqin Xu 6
1 UMR7578 CNRS, Institut de Physique du Globe de Paris, Paris, France.
2 GéosciencesMontpellier, Universite´ deMontpellier 2, CNRSUMR5243, Montpellier, France.
3 UMR5570 CNRS Universite´ Claude Bernard, Villeurbanne, France.
4 Universitat Potsdam, Institut fur Geowissenschaften, Potsdam, Germany.
5 Laboratoire de Géodynamique des Chaînes Alpines, Université Joseph Fourier, St. Martin d’Hères, France.
6 Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China.
Abstract:
The role of the Karakorum fault zone (KFZ) is
debated. South of 33°N, ongoing dextral-oblique slip along the SWedge
of theGar basin exhumes metamorphic and magmatic rocks of the Ayilari
range. Minerals have recorded a continuum of deformation from
temperatures
>600–400°C down to <250°C. The 40Ar/39Ar ages, the oldest being
21.2 ± 1.0 Ma, yield minimum estimates for the initiation of the KFZ.
These are in agreement with the U-Th/Pb ages constraining the onset of
deformation at ~25–22 Ma. Thermochronologic results show slow cooling
for the period ~21– 14 Ma, followed by rapid cooling between ~14 and 4
Ma. These data demonstrate that right-lateral motion was in progress in
the early Miocene and that shear continued at least until 4 Ma,
pointing to ~20 Ma of deformation along the fault. Greenschist facies
deformation superimposed upon the medium- to high-grade deformation
marks a kinematic change from pure dextral to dextral-normal motion
associated with the onset of rapid cooling. At the regional scale, the
coexistence of transtension in the Gar basin with transpression
documented along the Pangong range farther north suggests another
example of the ‘‘zipper tectonics’’ model developed along the Red River
fault. The kinematic shift induced the rise of the Ayilari range
starting at 16–12 Ma and the incision of major river courses. The Indus
River might have become captive of the relief at this time. The river’s
120 km of apparent offset implies dextral motion at a long-term rate of
~8.5 ± 1.5 mm yr-1.
Citation: Valli, F., N. Arnaud,
P.
H. Leloup, E. R. Sobel, G. Mahéo, R. Lacassin, S. Guillot, H. Li, P.
Tapponnier, and Z. Xu (2007), Twenty million years of continuous
deformation along the Karakorum fault, western Tibet: A
thermochronological analysis, Tectonics, 26, TC4004,
doi:10.1029/2005TC001913
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link for the final edited version (Tectonics WEB site) |
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P.H. Leloup page |