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40Ar/39Ar thermochronology of the Sulu terrane: Late Triassic exhumation of high- and ultrahigh-pressure rocks and implications for Mesozoic tectonics in East Asia

By
L.E. Webb
L.E. Webb
1
Department of Earth Sciences, Syracuse University, Syracuse, New York 13244, USA
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M.L. Leech
M.L. Leech
2
School of Earth Sciences, Stanford University, Stanford, California 94305, USA
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T.N. Yang
T.N. Yang
3
Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China
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Published:
January 01, 2006

Structural and thermochronological data from the Sulu terrane of eastern China document the exhumation of high-pressure and ultrahigh-pressure (UHP) metamorphic rocks to upper-crustal depths by ca. 206 Ma. 40Ar/39Ar ages from K-bearing phases record recrystallization and cooling through amphibolite- and upper greenschist–facies conditions during top-to-the-NW noncoaxial shear and suggest cooling rates on the order of 55 °C/m.y. Integration of the 40Ar/39Ar data with U/Pb constraints on the timing of UHP metamorphism yields vertical exhumation rates of >6 mm yr−1 from mantle to upper-crustal depths. Qualitative thermal models of metamorphic K-feldspars suggest transient reheating in the Jurassic of a magnitude insufficient to reset mica ages. The Yantai-Qingdao-Wulian fault that currently delineates the boundary between the Yangtze and Sino-Korean cratons was active in the Early Cretaceous as a top-to-the-W extensional detachment fault. The youngest phase of deformation recorded by the 40Ar/39Ar data is consistent with mid to Late Cretaceous deformation associated with the Tan-Lu fault. In total, the data reveal that high-pressure and UHP rocks of the Sulu terrane reached and resided at higher structural levels by the end of the Late Triassic relative to the high-pressure and UHP rocks presently exposed in the Dabie Shan. Thus, our 40Ar/39Ar data from the Sulu terrane provide the tightest constraints thus far on the timing and rates of exhumation of high-pressure and UHP rocks to upper-crustal depths in the orogen.

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GSA Special Papers

Ultrahigh-pressure metamorphism: Deep continental subduction

Bradley R. Hacker
Bradley R. Hacker
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William C. McClelland
William C. McClelland
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J.G. Liou
J.G. Liou
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Geological Society of America
Volume
403
ISBN print:
9780813724034
Publication date:
January 01, 2006

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