Large normal-sense displacement on the South Tibetan fault system in the eastern Himalaya

Cooper, Frances; Adams, B. A.; Edwards, C. S.; Hodges, Kip

doi:10.1130/g33318.1

Cited by 35 publications

(42 citation statements)

References 33 publications

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“…The High Himalayan Crystalline complex is bounded to the north by large-scale low-angle normal-sense faults and shear zones of the South Tibetan fault system (Hodges et al 1998;Dèzes et al 1999;Searle 1999;Cooper et al 2012). These faults resemble core complex detachments, and clearly played an important role in exhuming the metamorphic rocks beneath them.…”

Section: What Is a Metamorphic Core Complex?mentioning

confidence: 99%

Metamorphic core complexes: windows into the mechanics and rheology of the crust

Platt

Behr

Cooper

2014

JGS

138

131

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Metamorphic core complexes are products of normal-fault displacements sufficient to exhume rocks from below the brittle–ductile transition. These faults (detachments) may initiate within the brittle crust at steep angles, but they sole into the ductile middle crust, and during displacement rotate to gentler dips due to hanging-wall extension. The exhumed footwall commonly adopts an arched or domed geometry owing to flexural isostatic readjustment, and may be overlain by strongly extended upper crustal rocks that slipped on gently dipping, low-friction shallow segments of the detachment. Metamorphic rocks exhumed beneath the detachment record progressively increasing flow stress, strain localization and strain-rate with decreasing temperature, providing a window into physical conditions and deformational processes in the mid-crust. The metamorphic and deformational history of the footwall rocks may reflect tectonic processes that predate formation of the detachment fault, in addition to those accompanying exhumation. These processes may include diapiric emplacement of gneiss domes, or exhumation in a subduction channel, and may not be directly related to formation of the core complex. Factors favouring core complex formation are high gravitational potential energy of the extending crust, weak rheology and a change in the tectonic boundary conditions such as a cessation or slowing of plate convergence.

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Section: What Is a Metamorphic Core Complex?mentioning

confidence: 99%

Metamorphic core complexes: windows into the mechanics and rheology of the crust

Platt

Behr

Cooper

2014

JGS

138

131

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“…No identifiable stratigraphic offset below or within the TH section [ Long and McQuarrie , 2010], combined with minimal to diffuse changes in pressure or temperature along potential structural boundaries [ Kellett and Grujic , 2012], makes documenting the exact amount of displacement on the STDl, and how this amount may change along strike, difficult. Normal‐sense displacement estimates on this structure range from 20 to 65+ km [ Long and McQuarrie , 2010; Cooper et al , 2012].…”

Section: The Himalayan Thrust Belt In Bhutanmentioning

confidence: 99%

Variable shortening rates in the eastern Himalayan thrust belt, Bhutan: Insights from multiple thermochronologic and geochronologic data sets tied to kinematic reconstructions

Long¹,

McQuarrie²,

Tobgay³

et al. 2012

Tectonics

173

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We present data on the burial, displacement and exhumation history of the Himalayan fold‐thrust belt in eastern Bhutan. These data document the magnitude and timing of displacement of large, discrete structures and highlight temporal variability in shortening rates. Eight new40Ar/39Ar ages from white mica, 32 new zircon (U‐Th)/He ages, 7 new apatite fission track ages, and 1 new U‐Pb zircon (LA‐MC‐ICP‐MS) metamorphic rim growth age are combined with published cooling ages and deformation temperatures, and incremental shortening magnitudes from restorations of two published balanced cross sections, to illustrate the kinematic and temporal development of the Bhutan thrust belt. Integrating these data from ∼23 Ma to the present illustrates rapid horizontal shortening rates (28–35 mm/yr) between 23–20 Ma and 15–10 Ma, separated by more moderate rates (10–23 mm/yr). Shortening rates decrease significantly to 7–10 mm/yr (and possibly as low as 3–4 mm/yr) from 10 to 0 Ma. This decrease is interpreted to represent the onset of strain partitioning in the eastern part of the Himalayan‐Tibetan orogenic system, between shortening in the Bhutan thrust belt, uplift of the Shillong Plateau, and deformation and outward growth of the northern and eastern Tibetan Plateau. Within estimated error, horizontal shortening rates during emplacement of the Main Central thrust sheet and during construction of the upper Lesser Himalayan duplex approached India‐Asia tectonic velocities. Thus, for periods of time between ∼23–20 Ma and ∼15–10 Ma, the Bhutan thrust belt may have absorbed nearly all India‐Asian convergence at this longitude.

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“…(a) Geologic map from Cooper et al . [], modified in the Mount Jomolhari (Jh)‐Mount Jichu Drake (JD) range where the STFS is shown at a higher elevation than previously mapped. In this interpretation, the basal STFS detachment forms a continuous low‐angle surface separating isolated erosional remnants of the TSS in its hanging wall from high‐grade metamorphic rocks of the Chekha and GHS in its footwall.…”

Section: Structural Settingmentioning

confidence: 99%

“…It has also been proposed that the basal STFS detachment is a back thrust, kinematically linked to the north vergent Great Counter thrust system in southern Tibet [ Webb et al , , ; Yin , ; Yin et al , , ]. However, minimum constraints on STFS displacement of 65–170 km [ Cooper et al , , ; Law et al , ] are inconsistent with the limited displacement expected on such back thrusts.…”

Section: Introductionmentioning

confidence: 99%

Synchronous N-S and E-W extension at the Tibet-to-Himalaya transition in NW Bhutan

et al. 2015

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Despite~50 Myr of continuous continent-continent collision, contractional structures in the Himalayan-Tibetan orogen are today limited to the northern and southern margins of the system, while extension dominates much of the interior. On the Tibetan Plateau, Cenozoic E-W extension has been accommodated by strike-slip faults and extensional grabens, while N-S extension at the Tibet-to-Himalaya transition has been accommodated by the South Tibetan fault system (STFS). The genetic relationship between N-S and E-W extension is disputed, although age constraints indicate temporal overlap of at least 7 Myr. In NW Bhutan the two intersect where the STFS basal detachment is cut by the Yadong cross structure (YCS), an extensional half graben that provides a rare opportunity to constrain relative timings. We report U-Pb zircon dates from four STFS footwall leucogranites consistent with episodic magmatism during the middle-late Miocene and in situ U(-Th)-Pb monazite and xenotime dates from three metasedimentary rocks ranging from late Oligocene to middle Miocene. We suggest that amphibolite facies footwall metamorphism was ongoing at the time the basal STFS detachment initiated as a ductile structure in the middle-late Miocene. Late-stage granitic intrusions may reflect footwall melting during extensional exhumation along the STFS, but post-metamorphic and post-intrusion fabrics suggest that most displacement occurred after emplacement of the youngest granites. Some of the oldest YCS-related fabrics are found in a deformed 14 Ma leucogranite, implying middle Miocene ductile deformation. This observation, along with evidence for subsequent brittle YCS deformation, suggests that N-S and E-W extensional structures in the area had protracted and overlapping deformation histories.

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Large normal-sense displacement on the South Tibetan fault system in the eastern Himalaya

Cited by 35 publications

References 33 publications

Metamorphic core complexes: windows into the mechanics and rheology of the crust

Metamorphic core complexes: windows into the mechanics and rheology of the crust

Variable shortening rates in the eastern Himalayan thrust belt, Bhutan: Insights from multiple thermochronologic and geochronologic data sets tied to kinematic reconstructions

Synchronous N-S and E-W extension at the Tibet-to-Himalaya transition in NW Bhutan

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