Recycling of Paleotethyan oceanic crust: Geochemical record from postcollisional mafic igneous rocks in the Tongbai-Hong’an orogens

Research Article| January 01, 2017 Recycling of Paleotethyan oceanic crust: Geochemical record from postcollisional mafic igneous rocks in the Tongbai-Hong’an orogens Li-Qun Dai; Li-Qun Dai † Chinese Academy of Sciences (CAS) Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China †lqdai@ustc.edu.cn Search for other works by this author on: GSW Google Scholar Fei Zheng; Fei Zheng Chinese Academy of Sciences (CAS) Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China Search for other works by this author on: GSW Google Scholar Zi-Fu Zhao; Zi-Fu Zhao Chinese Academy of Sciences (CAS) Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China Search for other works by this author on: GSW Google Scholar Yong-Fei Zheng Yong-Fei Zheng Chinese Academy of Sciences (CAS) Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China Search for other works by this author on: GSW Google Scholar Author and Article Information Li-Qun Dai † Chinese Academy of Sciences (CAS) Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China Fei Zheng Chinese Academy of Sciences (CAS) Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China Zi-Fu Zhao Chinese Academy of Sciences (CAS) Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China Yong-Fei Zheng Chinese Academy of Sciences (CAS) Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China †lqdai@ustc.edu.cn Publisher: Geological Society of America Received: 21 Nov 2015 Revision Received: 29 Jun 2016 Accepted: 05 Aug 2016 First Online: 02 Jun 2017 Online Issn: 1943-2674 Print Issn: 0016-7606 © 2016 Geological Society of America GSA Bulletin (2017) 129 (1-2): 179–192. https://doi.org/10.1130/B31461.1 Article history Received: 21 Nov 2015 Revision Received: 29 Jun 2016 Accepted: 05 Aug 2016 First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Li-Qun Dai, Fei Zheng, Zi-Fu Zhao, Yong-Fei Zheng; Recycling of Paleotethyan oceanic crust: Geochemical record from postcollisional mafic igneous rocks in the Tongbai-Hong’an orogens. GSA Bulletin 2017;; 129 (1-2): 179–192. doi: https://doi.org/10.1130/B31461.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Plate tectonics can develop from oceanic subduction to continental collision, with disappearance of presubducted oceanic crust in continental subduction zones. This is typical for collisional orogens where Tethyan oceanic crust was consumed during continental convergence, with recycling of the Tethyan oceanic crust into the mantle. However, it is difficult to trace the geochemical signature of the previously subducted oceanic crust in collisional orogens. Postcollisional mafic igneous rocks in the Tongbai-Hong’an orogens provide a geochemical record of crust-mantle interaction during Paleotethyan oceanic subduction preceding the Triassic continental collision. These mafic igneous rocks were emplaced in the Cretaceous after continental collision and exhibit oceanic-island basalt (OIB)–like trace-element distribution patterns, with enrichment of large ion lithophile elements (LILEs) and light rare earth elements (LREEs) but no depletion of high field strength elements (HFSEs). They also show relatively depleted whole-rock Sr-Nd-Hf isotope compositions, with initial 87Sr/86Sr ratios of 0.7043–0.7050, εNd(t) values of –1.8–4.5, and εHf(t) values of 4.7–10.3. Such geochemical features indicate their origin from a juvenile mantle source that contained subducted oceanic crust–derived material. Thus, we suggest that the mantle source was generated by a melt-peridotite reaction at the slab-mantle interface in the Paleotethyan oceanic subduction channel during continental collision. The original peridotite would have been characterized by depletion of melt-mobile incompatible trace elements and radiogenic Sr-Nd-Hf isotopes, corresponding to the juvenile subarc lithospheric mantle. In contrast, the subducted crust–derived material would have been characterized by enrichment of LILEs and LREEs but no depletion of HFSEs, corresponding to felsic melts that were derived from partial melting of the subducting Paleotethyan oceanic basalt and sediment outside the rutile stability field. As such, the melt-peridotite reaction would generate pyroxenite-rich ultramafic metasomatites in the lower part of the mantle wedge, with relative enrichment of LILEs and LREEs but no depletion of HFSEs. In this model, partial melting of the metasomatites gave rise to the postcollisional mafic igneous rocks in the Tongbai-Hong’an orogens. Therefore, the postcollisional mafic igneous rocks record the recycling of Paleotethyan oceanic crust in the collisional orogen. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.