HP–UHP Metamorphism and Tectonic Evolution of Orogenic Belts
High pressure (HP) and ultrahigh pressure (UHP) metamorphic rocks play a key role in understanding the tectonic evolution of orogenic belts. They have typically experienced complex changes during subduction and exhumation processes arising from recrystallization, deformation, fluid–rock interactions and even partial melting, and may therefore carry valuable records of evolving geodynamic systems in an orogenic belt. This special publication addresses the current work on HP–UHP metamorphism and its relation to the tectonic evolution of orogenic belts.
This special publication contains fifteen papers covering the important orogenic belts of the Himalaya, Dabie–Sulu, Tian Shan, North Qaidam and others that have been grouped into three parts: (I) new developments in the determination of metamorphic pressure–temperature (PT) conditions and their timing, (II) overview papers of well-known HP–UHP metamorphic belts and (III) research papers for some newly discovered HP–UHP belts.
Constraining the age of high-pressure metamorphism of paragneisses from the Eastern Himalayan Syntaxis using zircon petrochronology and phase equilibria
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Published:January 01, 2019
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CiteCitation
Zuolin Tian, Zeming Zhang, Xin Dong, 2019. "Constraining the age of high-pressure metamorphism of paragneisses from the Eastern Himalayan Syntaxis using zircon petrochronology and phase equilibria", HP–UHP Metamorphism and Tectonic Evolution of Orogenic Belts, Lifei Zhang, Zeming Zhang, Hans-Peter Schertl, Chunjing Wei
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Abstract
The metamorphic evolution of the Eastern Himalayan Syntaxis (EHS) is of primary importance in understanding the tectonic framework of the India–Asia collision. However, the age of formation and exhumation of the high-pressure granulites from the EHS remains controversial. In this paper, we report the age of metamorphism of high-pressure (HP) granulite-facies paragneisses from the Namche Barwa Complex (NBC). These paragneisses consist of variable proportions of garnet, biotite, plagioclase, K-feldspar, quartz, rutile and ilmenite. Using phase equilibrium modelling of garnet growth combined with partitioning of rare earth elements (REEs) between zircon and garnet, we link multistage zircon growth to garnet growth to date the prograde stage to the interval 32.6–25.2 Ma, the pressure peak to c. 25–24 Ma and the retrograde stage to the interval 23.5–13.1 Ma. Taking into account published ages from the literature, for the NBC we propose that the prograde to peak metamorphism persisted until c. 25–24 Ma. This was followed by exhumation and melt crystallization during the interval 24–8 Ma, and cooling through the amphibolite facies after c. 8 Ma.
- absolute age
- Asia
- Cenozoic
- China
- crystal chemistry
- dates
- Far East
- garnet group
- geochemistry
- gneisses
- high pressure
- high-grade metamorphism
- Himalayas
- major elements
- metals
- metamorphic rocks
- metamorphism
- metasedimentary rocks
- mineral composition
- models
- nesosilicates
- Oligocene
- orthosilicates
- P-T conditions
- Paleogene
- paragneiss
- phase equilibria
- pressure
- rare earths
- silicates
- syntaxis
- Tertiary
- textures
- Tibetan Plateau
- U/Pb
- upper Oligocene
- zircon
- zircon group
- eastern Himalayas
- Namche Barwa Complex