Thermochronologic constraints on the slip history of the South Tibetan detachment system in the Everest region, southern Tibet

Mary Hannah Schultz, Kip Hodges, Todd A. Ehlers, Matthijs Van Soest, Jo Anne Wartho

Research output: Contribution to journalArticle

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Abstract

North-dipping, low-angle normal faults of the South Tibetan detachment system (STDS) are tectonically important features of the Himalayan–Tibetan orogenic system. The STDS is best exposed in the N–S-trending Rongbuk Valley in southern Tibet, where the primary strand of the system – the Qomolangma detachment – can be traced down dip from the summit of Everest for a distance of over 30 km. The metamorphic discontinuity across this detachment implies a large net displacement, with previous studies suggesting >200 km of slip. Here we refine those estimates through thermal–kinematic modeling of new (U–Th)/He and 40Ar/39Ar data from deformed footwall leucogranites. While previous studies focused on the early ductile history of deformation along the detachment, our data provide new insights regarding the brittle–ductile to brittle slip history. Thermal modeling results generated with the program QTQt indicate rapid, monotonic cooling from muscovite 40Ar/39Ar closure (ca. 15.4–14.4 Ma at ca. 490 °C) to zircon (U–Th)/He closure (ca. 14.3–11.0 Ma at ca. 200 °C), followed by slower cooling to apatite (U–Th)/He closure at ca. 9–8 Ma (at ca. 70 °C). Although previous work has suggested that ductile slip on the detachment lasted only until ca. 15.6 Ma, thermal–kinematic modeling of our new data suggests that rapid (ca. 3–4 km/Ma) tectonic exhumation by brittle–ductile to brittle fault slip continued to at least ca. 13.0 Ma. Much lower modeled exhumation rates (≤0.5 km/Ma) after ca. 13 Ma are interpreted to reflect erosional denudation rather than tectonic exhumation. Projection of fault-related exhumation rates backward through time suggests total slip of ca. 61 to 289 km on the Qomolangma detachment, with slightly more than a third of that slip occurring under brittle–ductile to brittle conditions.

Original languageEnglish (US)
Pages (from-to)105-117
Number of pages13
JournalEarth and Planetary Science Letters
Volume459
DOIs
StatePublished - Feb 1 2017

Fingerprint

Tibet
Tectonics
detachment
slip
Fault slips
exhumation
histories
Cooling
Apatites
history
closures
modeling
cooling
tectonics
fault slip
denudation
footwall
muscovite
normal fault
apatite

Keywords

  • detachment
  • exhumation
  • Himalaya
  • low-temperature thermochronology
  • thermal–kinematic modeling

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

Thermochronologic constraints on the slip history of the South Tibetan detachment system in the Everest region, southern Tibet. / Schultz, Mary Hannah; Hodges, Kip; Ehlers, Todd A.; Van Soest, Matthijs; Wartho, Jo Anne.

In: Earth and Planetary Science Letters, Vol. 459, 01.02.2017, p. 105-117.

Research output: Contribution to journalArticle

Schultz, Mary Hannah ; Hodges, Kip ; Ehlers, Todd A. ; Van Soest, Matthijs ; Wartho, Jo Anne. / Thermochronologic constraints on the slip history of the South Tibetan detachment system in the Everest region, southern Tibet. In: Earth and Planetary Science Letters. 2017 ; Vol. 459. pp. 105-117.
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