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Low temperature eclogite facies rocks discovered in the Eastern Himalayan Syntaxis: Poly-cyclic metamorphic evolution and implications |
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| Authors: | Wangchao Li Changqing Yin Zeming Zhang Peter A Cawood Shun Li Jian Zhang Huixia Ding Jiahui Qian Yanling Zhang |
| Institution: | 1. School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou, China
Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China;2. School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou, China;3. Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China School of the Earth and Resources, China University of Geosciences, Beijing, China;4. School of Earth, Atmosphere & Environment, Monash University, Melbourne, Victoria, Australia;5. School of Oceanography, Shanghai Jiao Tong University, Shanghai, China;6. School of the Earth and Resources, China University of Geosciences, Beijing, China |
| Abstract: | We report the first occurrence of poly-cyclic high-pressure low-temperature (HP-LT) rocks from the easternmost Indus-Yarlung suture zone, formed during subduction of Neo-Tethyan oceanic lithosphere. Petrology, mineral composition and P–T pseudosection modelling reveal two low-temperature eclogite facies metamorphic events with an initial high-pressure P–T condition of 16.4–18.7 kbar and 510–520°C, exhumation to 10.5–12.0 kbar and 580–590°C and a subsequent second high-pressure P–T condition of ~16 kbar and ~560°C and exhumation to ≤9 kbar and ≤600°C. This history implies a complex ‘yo-yo type’ P–T path. In situ monazite dating and textural relationships show that late-stage exhumation, cooling and garnet breakdown occurred at c. ~25–22 Ma. We interpret the first burial event to represent subduction of the Neo-Tethys Ocean at the eastern Indus-Yarlung suture zone. Initial exhumation, reburial and final exhumation represent material transport in a large-scale convective circulation system in the subduction channel. Convective overturn in the subduction channel evidently serves both as a mechanism to produce poly-cyclic metamorphism and to exhume LT eclogite facies rocks. |
| Keywords: | Eastern Himalayan Syntaxis LT eclogite facies rock poly-cyclic metamorphism P–T path subduction channel |