Cooling age record of domal uplift in the core of the Higher Himalayan Crystallines (HHC), southwest Zanskar, India |
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| Authors: | Rasoul B Sorkhabi Arvind K Jain Tetsumaru Itaya Shiro Fukui Nand Lal Ashok Kumar |
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| Institution: | (1) Department of Geology, Arizona State University, 85287-1404 Tempe, AZ, USA;(2) Department of Earth Sciences, University of Roorkee, 247667 Roorkee, U.P., India;(3) Hiruzen Research Institute, Okayama University of Science, 1-1 Ridai-cho, 700 Okayama, Japan;(4) Department of Geophysics, Kurukshetra University, 132119 Kurukshetra, India |
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| Abstract: | The cooling and tectonic history of the Higher Himalayan Crystallines (HHC) in southwest Zanskar (along the Kishtwar-Padam
traverse) is constrained by K-Ar biotite and fission-track (FT) apatite and zircon ages. A total of nine biotite samples yields
ages in the range of 14–24 Ma, indicating the post-metamorphic cooling of these rocks through ∼ 300°C in the Miocene. Overall,
the ages become younger away from the Zanskar Shear Zone (ZSZ), which marks the basement-cover detachment fault between the
HHC and the Tethyan sedimentary zone, towards the core of the HHC. The same pattern is also observed for the FT apatite ages,
which record the cooling of the rocks through ∼ 120°C. The apatite ages range from 11 Ma in the vicinity of the ZSZ to 4 Ma
at the granitic core of the HHC. This pattern of discordant cooling ages across the HHC in southwest Zanskar reveals an inversion
of isotherms due to fast uplift-denudation (hence cooling) of the HHC core, which is, in turn, related to domal uplift within
the HHC. The Chisoti granite gneiss is the exposed domal structure along the studied traverse. Cooling history of two granite
gneisses at the core of the HHC is also quantified with the help of the biotite, zircon and apatite ages; the time-temperatures
thus obtained indicate a rapid pulse of cooling at ∼ 6 Ma, related to accelerated uplift-denudation of the HHC core at this
time. Long-term denudation rates of 0.5–0.7 mm/yr are estimated for the high-grade rocks of the Higher Himalaya in southwest
Zanskar over the past 4.0–5.5 m.yr. |
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| Keywords: | The Himalaya Zanskar thermochronology Himalayan metamorphism domal uplift |
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