Tectonic evolution of the early Mesozoic blueschist-bearing Qiangtang metamorphic belt, central Tibet

Paul A Kapp, An Yin, Craig E. Manning, T. Mark Harrison, Michael H. Taylor, Lin Ding

Research output: Contribution to journalArticle

318 Citations (Scopus)

Abstract

A >500-km-long east-west trending metamorphic belt in the Qiangtang terrane of central Tibet consists of tectonic melange that occurs in the footwalls of Late Triassic-Early Jurassic domal low-angle normal faults. The melange is comprised of a strongly deformed matrix of metasedimentary and mafic schists that encloses lesser-deformed blocks of metabasites, Carboniferous-Triassic metasedimentary rocks, and early Paleozoic gneiss. Both the blocks and melange matrix exhibit greenschist, epidote-blueschist, and locally, epidote-amphibolite facies mineral assemblages. Thermobarometry reveals that the metamorphic belt experienced pressures of >10 kbar. Maximum equilibration temperatures for mafic schists in the melange matrix decrease from east to west, from ∼660°C near Shuang Hu (33°N, 89°E), ∼500°C near Rongma (33°N, 87°E), to ∼425°C near Gangma Co (34°N, 84°E). Equilibration at consistently high pressures over a large range of temperatures is compatible with metamorphism of Qiangtang melange within a low-angle subduction zone beneath a continental margin. Coupled structural, thermobarometric, and 40Ar/39Ar studies suggest that Qiangtang melange was exhumed in an intracontinental setting from depths of >35 km to upper crustal levels in <12 Myr by Late Triassic-Early Jurassic crustal-scale normal faulting. Detrital zircons from metasandstones within the melange matrix yield U-Pb ion-microprobe ages that range from early Paleozoic to Early Archean, and could have been sourced from terranes to the north of the Jinsha suture. Our results support a model in which Qiangtang melange was underthrust ∼200 km beneath the Qiangtang terrane during early Mesozoic flat-slab southward subduction of Paleo-Tethyan oceanic lithosphere along the Jinsha suture. This model predicts that significant portions of the central Tibetan continental mantle lithosphere were removed during early Mesozoic low-angle oceanic subduction and that the present-day central Tibetan deeper crust includes large volumes of underthrust early Mesozoic melange.

Original languageEnglish (US)
JournalTectonics
Volume22
Issue number4
StatePublished - Aug 2003
Externally publishedYes

Fingerprint

Bearings (structural)
Tibet
blueschist
melange
Tectonics
tectonic evolution
tectonics
Faulting
schist
matrices
lithosphere
Minerals
Rocks
Ions
Temperature
gneiss
terrane
matrix
Triassic
continental shelves

Keywords

  • Blueschist
  • Exhumation
  • Melange
  • Metamorphic core complex
  • Subduction
  • Tibet

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Kapp, P. A., Yin, A., Manning, C. E., Harrison, T. M., Taylor, M. H., & Ding, L. (2003). Tectonic evolution of the early Mesozoic blueschist-bearing Qiangtang metamorphic belt, central Tibet. Tectonics, 22(4).

Tectonic evolution of the early Mesozoic blueschist-bearing Qiangtang metamorphic belt, central Tibet. / Kapp, Paul A; Yin, An; Manning, Craig E.; Harrison, T. Mark; Taylor, Michael H.; Ding, Lin.

In: Tectonics, Vol. 22, No. 4, 08.2003.

Research output: Contribution to journalArticle

Kapp, PA, Yin, A, Manning, CE, Harrison, TM, Taylor, MH & Ding, L 2003, 'Tectonic evolution of the early Mesozoic blueschist-bearing Qiangtang metamorphic belt, central Tibet', Tectonics, vol. 22, no. 4.
Kapp, Paul A ; Yin, An ; Manning, Craig E. ; Harrison, T. Mark ; Taylor, Michael H. ; Ding, Lin. / Tectonic evolution of the early Mesozoic blueschist-bearing Qiangtang metamorphic belt, central Tibet. In: Tectonics. 2003 ; Vol. 22, No. 4.
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abstract = "A >500-km-long east-west trending metamorphic belt in the Qiangtang terrane of central Tibet consists of tectonic melange that occurs in the footwalls of Late Triassic-Early Jurassic domal low-angle normal faults. The melange is comprised of a strongly deformed matrix of metasedimentary and mafic schists that encloses lesser-deformed blocks of metabasites, Carboniferous-Triassic metasedimentary rocks, and early Paleozoic gneiss. Both the blocks and melange matrix exhibit greenschist, epidote-blueschist, and locally, epidote-amphibolite facies mineral assemblages. Thermobarometry reveals that the metamorphic belt experienced pressures of >10 kbar. Maximum equilibration temperatures for mafic schists in the melange matrix decrease from east to west, from ∼660°C near Shuang Hu (33°N, 89°E), ∼500°C near Rongma (33°N, 87°E), to ∼425°C near Gangma Co (34°N, 84°E). Equilibration at consistently high pressures over a large range of temperatures is compatible with metamorphism of Qiangtang melange within a low-angle subduction zone beneath a continental margin. Coupled structural, thermobarometric, and 40Ar/39Ar studies suggest that Qiangtang melange was exhumed in an intracontinental setting from depths of >35 km to upper crustal levels in <12 Myr by Late Triassic-Early Jurassic crustal-scale normal faulting. Detrital zircons from metasandstones within the melange matrix yield U-Pb ion-microprobe ages that range from early Paleozoic to Early Archean, and could have been sourced from terranes to the north of the Jinsha suture. Our results support a model in which Qiangtang melange was underthrust ∼200 km beneath the Qiangtang terrane during early Mesozoic flat-slab southward subduction of Paleo-Tethyan oceanic lithosphere along the Jinsha suture. This model predicts that significant portions of the central Tibetan continental mantle lithosphere were removed during early Mesozoic low-angle oceanic subduction and that the present-day central Tibetan deeper crust includes large volumes of underthrust early Mesozoic melange.",
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