Mantle Hg isotopic heterogeneity and evidence of oceanic Hg recycling into the mantle
NATURE COMMUNICATIONS(2022)
摘要
The geochemical cycle of mercury in Earth’s surface environment (atmosphere, hydrosphere, biosphere) has been extensively studied; however, the deep geological cycling of this element is less well known. Here we document distinct mass-independent mercury isotope fractionation (expressed as Δ 199 Hg) in island arc basalts and mid-ocean ridge basalts. Both rock groups show positive Δ 199 Hg values up to 0.34‰ and 0.22‰, respectively, which deviate from recent estimates of the primitive mantle (Δ 199 Hg: 0.00 ± 0.10‰, 2 SD) 1 . The positive Δ 199 Hg values indicate recycling of marine Hg into the asthenospheric mantle. Such a crustal Hg isotope signature was not observed in our samples of ocean island basalts and continental flood basalts, but has recently been identified in canonical end-member samples of the deep mantle 1 , therefore demonstrating that recycling of mercury can affect both the upper and lower mantle. Our study reveals large-scale translithospheric Hg recycling via plate tectonics.
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关键词
oceanic hg recycling,isotopic heterogeneity
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