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Progressive development of E-W extension across the Tibetan plateau: A case study of the Thakkhola graben, west-central Nepal
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  • Kyle Larson,
  • Alex Brubacher,
  • John Cottle,
  • William Andrew Matthews,
  • Alfredo Camacho
Kyle Larson
University of British Columbia

Corresponding Author:[email protected]

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Alex Brubacher
University of British Columbia
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John Cottle
NERC Isotope Geosciences Laboratory
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William Andrew Matthews
University of Calgary
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Alfredo Camacho
University of Manitoba
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The Thakkhola graben is a large-scale N-S striking, E-W structure located in west-central Nepal that was actively extending ca. 17 Myr ago. New multi-system geochronological data from the immediate footwall of the Dangardzong fault, the main graben-forming structure in the Thakkhola, outline decelerating cooling paths. The average cooling rate in the immediate footwall of the Dangardzong fault progressively decreases from 55 ± 10 ˚C/Ma in the early Miocene (~ 22-13 Ma, monazite U-Th/Pb, mica Ar/Ar and zircon U-Th/He), to 23 ± 8 ˚C/Ma in the middle to late Miocene (~13-8 Ma, zircon and apatite U-Th/He), and finally to 10 ± 2 ˚C/Ma from 8 Ma to present day (cooling post apatite U-Th/He closure). The deceleration in cooling rate is interpreted to reflect the widespread development of N-S striking graben structures in the Tibetan plateau in the middle Miocene and the progressive partitioning of strain away from the Thakkhola into other, younger, extensional features.