Is the HP–UHP Hong’an–Dabie–Sulu orogen a piercing point for offset on the Tan–Lu fault? |
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| Institution: | 1. College of Earth Sciences, Jilin University, Changchun 130061, China;2. State Key Laboratory of Geological Processes and Mineral Resources, Faculty of Earth Resources, and Collaborative Innovation Center for Exploration of Strategic Mineral Resources, China University of Geosciences, Wuhan 430074, China;3. State Key Laboratory for Mineral Deposits Research, Department of Earth Sciences, Nanjing University, Nanjing 210093, China;1. Department of Earth Sciences and Institute of Energy Sciences, Nanjing University, Nanjing 210093, China;2. Resources and Environment Institute, Southwest Petroleum University, Chengdu 610500, China;3. The Southwest Branch of SINOPEC, Chengdu 610016, China;1. School of Resource and Environmental Engineering, Hefei University of Technology, Hefei 230009, China;2. Nanjing Institute of Geology and Mineral Resources, China Geological Survey, Nanjing 210016, China;1. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 10029, China;2. Géosciences Montpellier, UMR-CNRS 5243, Université de Montpellier 2, Pl. E.—Bataillon, F-34095, Montpellier Cedex, France |
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| Abstract: | The Tan–Lu fault is a major strike-slip fault in eastern China that appears to offset the high-grade rocks of the Hong’an–Dabie–Sulu orogen left-laterally ∼540 km. We evaluate models for the collision between the South and North China blocks, published radiometric dates recording HP–UHP metamorphism and exhumation in the Hong’an–Dabie and Sulu terranes, and the timing of sinistral motion on the Tan–Lu fault to evaluate whether UHP rocks provide a piercing point for offset on the Tan–Lu fault. UHP metamorphism in Hong’an–Dabie was concurrent with Sulu based on U–Pb dating of coesite-bearing domains of zircon at 244 ± 5–226 ± 2 Ma for Hong’an–Dabie and 243 ± 4–225 ± 2 Ma for Sulu. Retrograde metamorphism began c. 220 Ma for both Hong’an–Dabie and Sulu, but retrograde zircon growth ended c. 214 Ma in Hong’an–Dabie and continued until c. 202 Ma in Sulu based on U–Pb dating of zircon domains external to coesite-bearing domains. Structures in Sulu are rotated 25° counter-clockwise from, but are broadly similar to, Hong’an–Dabie suggesting the two areas have a common Triassic orogenic history that pre-dates motion on the Tan–Lu fault, and that is consistent with paleomagnetic studies. We constructed a pre-Cretaceous restoration of the Hong’an–Dabie–Sulu belt that moves the Sulu terrane south, aligning the suture and the eclogite-facies isograd, and rotates Sulu c. 25° clockwise to re-align structures with Hong’an–Dabie. Our restoration is supported by published data and shows that the Hong’an–Dabie–Sulu orogen is a piercing point for post-collisional offset on the Tan–Lu fault and that these regions shared a common subduction–exhumation history. The Tan–Lu fault did not play a significant role in the Hong’an–Dabie–Sulu collision and likely developed later, in the Early Cretaceous. |
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