Nonglacial origin for low- 18O Neoproterozoic magmas in the South China Block: Evidence from new in-situ oxygen isotope analyses using SIMS

Research Article| August 01, 2011 Nonglacial origin for low-δ18O Neoproterozoic magmas in the South China Block: Evidence from new in-situ oxygen isotope analyses using SIMS Xuan-Ce Wang; Xuan-Ce Wang * 1State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China2Institute for Geoscience Research, Department of Applied Geology, Curtin University, GPO Box U1987, Perth, WA 6845, Australia3School of Earth and Environment, the University of Western Australia, Crawley, WA 6009, Australia *E-mail: X.Wang3@curtin.edu.au. Search for other works by this author on: GSW Google Scholar Zheng-Xiang Li; Zheng-Xiang Li 2Institute for Geoscience Research, Department of Applied Geology, Curtin University, GPO Box U1987, Perth, WA 6845, Australia Search for other works by this author on: GSW Google Scholar Xian-Hua Li; Xian-Hua Li 1State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China Search for other works by this author on: GSW Google Scholar Qiu-Li Li; Qiu-Li Li 1State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China Search for other works by this author on: GSW Google Scholar Guo-Qiang Tang; Guo-Qiang Tang 1State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China Search for other works by this author on: GSW Google Scholar Qi-Rui Zhang; Qi-Rui Zhang 1State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China Search for other works by this author on: GSW Google Scholar Yu Liu Yu Liu 1State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China Search for other works by this author on: GSW Google Scholar Author and Article Information Xuan-Ce Wang * 1State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China2Institute for Geoscience Research, Department of Applied Geology, Curtin University, GPO Box U1987, Perth, WA 6845, Australia3School of Earth and Environment, the University of Western Australia, Crawley, WA 6009, Australia Zheng-Xiang Li 2Institute for Geoscience Research, Department of Applied Geology, Curtin University, GPO Box U1987, Perth, WA 6845, Australia Xian-Hua Li 1State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China Qiu-Li Li 1State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China Guo-Qiang Tang 1State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China Qi-Rui Zhang 1State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China Yu Liu 1State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing 100029, China *E-mail: X.Wang3@curtin.edu.au. Publisher: Geological Society of America Received: 12 Dec 2010 Revision Received: 11 Mar 2011 Accepted: 13 Mar 2011 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2011 Geological Society of America Geology (2011) 39 (8): 735–738. https://doi.org/10.1130/G31991.1 Article history Received: 12 Dec 2010 Revision Received: 11 Mar 2011 Accepted: 13 Mar 2011 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Xuan-Ce Wang, Zheng-Xiang Li, Xian-Hua Li, Qiu-Li Li, Guo-Qiang Tang, Qi-Rui Zhang, Yu Liu; Nonglacial origin for low-δ18O Neoproterozoic magmas in the South China Block: Evidence from new in-situ oxygen isotope analyses using SIMS. Geology 2011;; 39 (8): 735–738. doi: https://doi.org/10.1130/G31991.1 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 SocietyGeology Search Advanced Search Abstract Low-δ18O signatures in supracrustal rocks have been used as geochemical proxies for cold paleoclimates, e.g., glaciations. Unusual low-δ18O values found in Neoproterozoic igneous rocks in parts of the South China Block have thus been genetically linked to Neoproterozoic glaciation events. However, we report here new oxygen isotope compositions from Neoproterozoic magmatic zircons in central southern China using in-situ techniques that argue against such an interpretation. Our results show that (1) low-δ18O magmatic zircons started to appear in the South China Block from ca. 870 Ma, coinciding with the tectonic switching from Sibao orogenesis to postorogenic extension, which occurred more than 150 m.y. prior to the first glaciation event. The most abundant low-δ18O magmatic zircons have ages of 800–700 Ma. (2) The 830–700 Ma magmatic zircons are characterized by their bimodal nature of oxygen isotope compositions, i.e., mantle-like δ18O values (+4.4‰ to +5.8‰) and high-δ18O values (+9.3‰ to +10.8‰). (3) A sharp temporal change in maximum zircon δ18O values in the South China Block coincided with the onset of continental rifting and the possible arrival of a plume head. (4) No negative δ18O zircons have been identified in this study, contrary to previous studies. These features strongly argue against a glaciation origin for low to negative δ18O values in Neoproterozoic magmatic zircons from southern China. We propose that two stages of high-temperature water-magma interaction during plume-driven magmatism and continental rifting best explain the low-δ18O magmas. The most important implication of this study is that formation of such low-δ18O magmatic zircons was not necessarily related to glacial events and should not be used as a geochemical proxy for a cold paleoclimate. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.