Magnesium isotope evidence for a recycled origin of cratonic eclogites

Research Article| December 01, 2015 Magnesium isotope evidence for a recycled origin of cratonic eclogites Shui-Jiong Wang; Shui-Jiong Wang * 1Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195-1310, USA2State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China *E-mails: sxw057@gmail.com; fteng@u.washington.edu Search for other works by this author on: GSW Google Scholar Fang-Zhen Teng; Fang-Zhen Teng * 1Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195-1310, USA *E-mails: sxw057@gmail.com; fteng@u.washington.edu Search for other works by this author on: GSW Google Scholar Roberta L. Rudnick; Roberta L. Rudnick 3Geochemical Laboratory, Department of Geology, University of Maryland, College Park, Maryland 20742, USA Search for other works by this author on: GSW Google Scholar Shu-Guang Li Shu-Guang Li 2State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China4CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, Anhui, China Search for other works by this author on: GSW Google Scholar Author and Article Information Shui-Jiong Wang * 1Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195-1310, USA2State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China Fang-Zhen Teng * 1Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195-1310, USA Roberta L. Rudnick 3Geochemical Laboratory, Department of Geology, University of Maryland, College Park, Maryland 20742, USA Shu-Guang Li 2State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China4CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, Anhui, China *E-mails: sxw057@gmail.com; fteng@u.washington.edu Publisher: Geological Society of America Received: 12 Aug 2015 Revision Received: 01 Oct 2015 Accepted: 07 Oct 2015 First Online: 09 Mar 2017 Online Issn: 1943-2682 Print Issn: 0091-7613 © 2015 Geological Society of America Geology (2015) 43 (12): 1071–1074. https://doi.org/10.1130/G37259.1 Article history Received: 12 Aug 2015 Revision Received: 01 Oct 2015 Accepted: 07 Oct 2015 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Shui-Jiong Wang, Fang-Zhen Teng, Roberta L. Rudnick, Shu-Guang Li; Magnesium isotope evidence for a recycled origin of cratonic eclogites. Geology 2015;; 43 (12): 1071–1074. doi: https://doi.org/10.1130/G37259.1 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 The Mg isotopic compositions of garnet and clinopyroxene mineral separates and whole rocks from 21 xenolithic eclogites (11 low-MgO eclogites and 10 high-MgO eclogites) from the Koidu kimberlite complex, erupted within the Archean Man Shield, Sierra Leone, West Africa, provide new evidence bearing on the origin of cratonic eclogites. Garnet and clinopyroxene in both low-MgO and high-MgO eclogites generally record equilibrium inter-mineral Mg isotope partitioning, with δ26Mg varying from –2.15‰ to –0.46‰ in garnets and from –0.49‰ to +0.35‰ in clinopyroxenes. Bulk δ26Mg values (–1.38‰ to +0.05‰), constructed from garnet and clinopyroxene data, are similar to results from rock powders (–1.60‰ to +0.17‰), suggesting that kimberlite infiltration has had negligible influence on the Mg isotopic compositions of the xenoliths. The δ26Mg values of low-MgO eclogites (–0.80‰ to +0.05‰) exceed the range of mantle peridotite xenoliths (–0.25‰ ± 0.04‰), consistent with the eclogite’s derivation from recycled altered oceanic crust. Similarly variable δ26Mg values in high-MgO eclogites (–0.95‰ to –0.13‰), together with their high MgO and low FeO contents, suggest that high-MgO eclogites were produced by Mg-Fe exchange between partially molten low-MgO eclogites and surrounding peridotites. Our study shows that cratonic xenolithic eclogites preserve a record of Mg isotopic compositions produced by low-pressure, surficial isotope fractionations. The recycling of oceanic crust therefore increases the Mg isotope heterogeneity of the mantle. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.