title: A 'hidden' 18O-enriched reservoir in the sub-arc mantle.
abstract: Plate subduction continuously transports crustal materials with high-δ(18)O values down to the mantle wedge, where mantle peridotites are expected to achieve the high-δ(18)O features. Elevated δ(18)O values relative to the upper mantle value have been reported for magmas from some subduction zones. However, peridotites with δ(18)O values significantly higher than the well-defined upper mantle values have never been observed from modern subduction zones. Here we present in-situ oxygen isotope data of olivine crystals in Sailipu mantle xenoliths from South Tibet, which have been subjected to a long history of Tethyan subduction before the India-Asia collision. Our data identify for the first time a metasomatized mantle that, interpreted as the sub-arc lithospheric mantle, shows anomalously enriched oxygen isotopes (δ(18)O = +8.03 ± 0.28 ‰). Such a high-δ(18)O mantle commonly does not contribute significantly to typical island arc basalts. However, partial melting or contamination of such a high-δ(18)O mantle is feasible to account for the high-δ(18)O signatures in arc basalts.
authors.affiliation: State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.
authors.forename: Chuan-Zhou
authors.initials: CZ
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.
authors.forename: Fu-Yuan
authors.initials: FY
authors.lastname: Wu
authors.affiliation: Department of Geosciences, National Taiwan University, Taipei 10617.
authors.forename: Sun-Lin
authors.initials: SL
authors.lastname: Chung
authors.affiliation: State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.
authors.forename: Qiu-Li
authors.initials: QL
authors.lastname: Li
authors.affiliation: State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.
authors.forename: Wei-Dong
authors.initials: WD
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.
authors.forename: Wei-Qiang
authors.initials: WQ
authors.lastname: Ji
mesh_terms: D018534:Earth, Planet; D019015:Geologic Sediments / Q000032:analysis* / Q000737:chemistry*; D058085:Iron Compounds / Q000737:chemistry*; D017616:Magnesium Compounds / Q000737:chemistry*; D010103:Oxygen Isotopes / Q000032:analysis*; D017640:Silicates / Q000737:chemistry*
chemical_list: D058085:Iron Compounds; D017616:Magnesium Compounds; D010103:Oxygen Isotopes; D017640:Silicates; C060346:basalt; C034475:olivine