Is the HP-UHP Hong¡¯an-Dabie-Sulu orogen a piercing point for offset on the Tan-Lu fault?

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• 作者：Mary L. Leech^a ; ^{leech@sfsu.edu} ; Laura E. Webb^b ; ^{lewebb@uvm.edu}
• 关键词：Ultrahigh-pressure metamorphism ; Hong&rsquo ; an&ndash ; Dabie&ndash ; Sulu ; Tan&ndash ; Lu fault ; Eastern China ; Collision model
• 刊名：Journal of Asian Earth Sciences
• 出版年：2013
• 出版时间：15 February, 2013
• 年：2013
• 卷：63
• 期：Complete
• 页码：112-129
• 全文大小：2178 K

文摘

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 ¡À 5-226 ¡À 2 Ma for Hong¡¯an-Dabie and 243 ¡À 4-225 ¡À 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¡ã 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¡ã 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.