title: Tracing carbonate-silicate interaction during subduction using magnesium and oxygen isotopes.
abstract: Subduction of carbonates and carbonated eclogites into the mantle plays an important role in transporting carbon into deep Earth. However, to what degree isotopic exchanges occur between carbonate and silicate during subduction remains unclear. Here we report Mg and O isotopic compositions for ultrahigh pressure metamorphic marbles and enclosed carbonated eclogites from China. These marbles include both calcite- and dolomite-rich examples and display similar O but distinct Mg isotopic signatures to their protoliths. Their δ(26)Mg values vary from -2.508 to -0.531‰, and negatively correlate with MgO/CaO ratios, unforeseen in sedimentary carbonates. Carbonated eclogites have extremely heavy δ(18)O (up to +21.1‰) and light δ(26)Mg values (down to -1.928‰ in garnet and -0.980‰ in pyroxene) compared with their protoliths. These unique Mg-O isotopic characteristics reflect differential isotopic exchange between eclogites and carbonates during subduction, making coupled Mg and O isotopic studies potential tools for tracing deep carbon recycling.
authors.affiliation: 1] State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China [2] Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Shui-Jiong
authors.initials: SJ
authors.lastname: Wang
authors.affiliation: Isotope Laboratory, Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Fang-Zhen
authors.initials: FZ
authors.lastname: Teng
authors.affiliation: 1] State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China [2] CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Shu-Guang
authors.initials: SG
authors.lastname: Li