Large garnet porphyroblast with an internal foliation of quartz and opaque inclusion trails defining a S1 foliation crenulated by a S2 foliation. S2 foliation wraps around garnet.

Middle Crustal Flow and Tectonic Evolution of Gneiss Domes, Southern Tibet

Project Summary

Gneiss domes are found in orogenic belts worldwide and are typically composed of a core of middle crustal rocks, including granitic migmatites or gneisses, structurally overlain by a mantle of high-grade metasedimentary rocks which in turn are overlain by unmetamorphosed rocks. A number of mechanisms have been proposed for the origin of gneiss domes, ranging from diapirism, crustal shortening, and crustal extension, to some combination of these processes. Each of these mechanisms, or combinations thereof, have dramatically different implications for the tectonic evolution of an orogen.

The North Himalayan gneiss domes, southern Tibet are a series of isolated domes that provide a window into the middle crust within the Tethyan Himalaya south of the Indus-Tsangpo Suture Zone and north of the Southern Tibetan detachment system. This project is an integrated (geologic mapping, structural and kinematic analyses, metamorphic petrology, thermochronology, and geochronology) investigation of the processes of ductile flow in the middle crust of southern Tibet, of the mechanisms by which these gneiss domes formed and were exhumed, and the implications of those mechanisms for the tectonic and geodynamic evolution of the India-Asia collision.

Research collaborators include: Yu Wang (China Univ. of Geosciences, China), Brad Hacker, Bill Dinklage, and Andy Calvert (UC Santa Barbara), Ann Blyth (Univ. of Southern California), Mike McWilliams (Stanford Univ.), Bill McClelland (Univ. of Idaho), Simon Wallis, Mutsuki Aoya, and Tetsuo Kawakami (Nagoya Univ., Japan), and Martin Whitehouse (Swedish Museum of Natural History).

Publications

• Langille, J., Lee, J., Hacker, B.R., and Seward, G., Middle crustal ductile deformation patterns in southern Tibet: Insights from vorticity studies in Mabja Dome , Journal of Structural Geology, in review.
• Kawakami, T., Aoya, M, Wallis, S.R., Lee, J., Terada, K., Wang, Y., and Heizler, M. 2007, Contact metamorphism in the Malashan dome, North Himalayan gneiss domes, southern Tibet: An example of shallow extensional tectonics in the Tethys Himalaya, Journal of Metamorphic Geology, v. 25, p. 831-853; doi:10.1111/j.1525-1314.2007.00731.x. [PDF] (The definitive version of this article is available at www.blackwell-synergy.com.)
• Lee, J. and Whitehouse, M.J., 2007, Onset of mid-crustal extensional flow in southern Tibet: Evidence from U/Pb zircon ages, Geology, v. 35, p. 45-48; doi: 10.1130/G22842A.1. [PDF]
• Lee, J., McClelland, W., Wang, Y., Blythe, A., and McWilliams, M., 2006, Oligocene-Miocene middle crustal flow in southern Tibet: Geochronologic studies in Mabja Dome: in Law, R.D., Searle, M.P. & Godin, L. (eds.), Channel Flow, Ductile Extrusion and Exhumation in Continental Collision Zones, Geological Society of London Special Publication, v. 268, p. 445-469. [PDF] (Copyright of the electronic version of this article is retained by The Geological Society of London).
• Aoya, M., Wallis, S.R., Kawakami, T., Lee, J., and Wang, Y., 2006, The Malashan metamorphic complex in southern Tibet: Comparative study with Kangmar Dome with special reference to kinematics of deformation and origin of associated granites: in Law, R.D., Searle, M.P. & Godin, L. (eds.), Channel Flow, Ductile Extrusion and Exhumation in Continental Collision Zones, Geological Society of London Special Publication, v. 268, p. 471-495. [PDF]
• Aoya, M., Wallis, S.R., Terada, K., Lee, J., Kawakami, T., Wang, Y., and Heizler, M., 2005, North-south extension in the Tibetan crust triggered by granite emplacement, Geology, v. 33, p. 853–856. [PDF]
• Lee, J., Hacker, B., and Wang, Y., 2004, Evolution of the North Himalayan gneiss domes: Structure and metamorphic studies in Mabja Dome, southern Tibet, Journal of Structural Geology, v. 26, p. 2297-2316. [PDF]
• Lee, J., Dinklage, W.S., Wang, Y., and Wan, J., 2002, Geology of the Kangmar Dome, southern Tibet with explanatory notes, Geological Society of America, Map and Chart Series MCH090, 1:50,000 scale, 8 p.
• Lee, J., Hacker, B.R., Dinklage, W.S., Wang, Y., Gans, P.B., Calvert, A., Wan, J., Chen, W., Blythe, A., and McClelland. W., 2000, Evolution of the Kangmar Dome, southern Tibet: Structural, petrologic, and thermochronologic constraints, Tectonics, v. 19, p. 872-896. [PDF]

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