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Published October 1, 2013 | Supplemental Material + Published
Journal Article Open

Low-temperature thermochronometry along the Kunlun and Haiyuan Faults, NE Tibetan Plateau: Evidence for kinematic change during late-stage orogenesis

Abstract

The Tibetan Plateau is a prime example of a collisional orogen with widespread strike-slip faults whose age and tectonic significance remain controversial. We present new low-temperature thermochronometry to date periods of exhumation associated with Kunlun and Haiyuan faulting, two major strike-slip faults within the northeastern margin of Tibet. Apatite and zircon (U-Th)/He and apatite fission-track ages, which record exhumation from ~2 to 6 km crustal depths, provide minimum bounds on fault timing. Results from Kunlun samples show increased exhumation rates along the western fault segment at circa 12–8 Ma with a possible earlier phase of motion from ~30–20 Ma, along the central fault segment at circa 20–15 Ma, and along the eastern fault segment at circa 8–5 Ma. Combined with previous studies, our results suggest that motion along the Haiyuan fault may have occurred as early as ~15 Ma along the western/central fault segment before initiating at least by 10–8 Ma along the eastern fault tip. We relate an ~250 km wide zone of transpressional shear to synchronous Kunlun and Haiyuan fault motion and suggest that the present-day configuration of active faults along the northeastern margin of Tibet was likely established since middle Miocene time. We interpret the onset of transpression to relate to the progressive confinement of Tibet against rigid crustal blocks to the north and expansion of crustal thickening to the east during the later stages of orogen development.

Additional Information

© 2013 American Geophysical Union. Received 20 January 2013; revised 4 July 2013; accepted 1 August 2013; published 1 October 2013. This work was supported by the NSF (grants EAR-0507431, EAR-0507788, EAR-0908711), the National Science Foundation of China (40234040), and by the State Key Laboratory of Earthquake Dynamics (LED2008A01). We thank Lindsay Hedges for assistance with sample analyses, and Nathan Harkins, Xuhua Shi, Katherine Dayem, Karen Lease, colleagues at the Lanzhou Institute of Seismology, Pei-Zhen Zhang and colleagues at the State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration for help with sample collection and field support. We also thank anonymous reviewers for thorough and instructive feedback that greatly improved the paper. We also acknowledge Nathan Niemi, Douglas Burbank, Zheng Dewen, and Peter Molnar for constructive dialogue regarding this work.

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Supplemental Material - SupplementaryMaterial.docx

Supplemental Material - TableS1.xlsx

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August 22, 2023
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