Heavy iron in large gem diamonds traces deep subduction of serpentinized ocean floor
Smith, E.M.; Ni, P.; Shirey, S.B.; Richardson, S.H.; Wang, W.; Shahar, A. (2021). Heavy iron in large gem diamonds traces deep subduction of serpentinized ocean floor. Science Advances 7(14): eabe9773. https://hdl.handle.net/10.1126/sciadv.abe9773
In: Science Advances. AAAS: New York. ISSN 2375-2548; e-ISSN 2375-2548, more
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| Authors | | Top |
- Smith, E.M.
- Ni, P.
- Shirey, S.B.
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- Richardson, S.H.
- Wang, W.
- Shahar, A.
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| Abstract |
Subducting tectonic plates carry water and other surficial components into Earth’s interior. Previous studies suggest that serpentinized peridotite is a key part of deep recycling, but this geochemical pathway has not been directly traced. Here, we report Fe-Ni–rich metallic inclusions in sublithospheric diamonds from a depth of 360 to 750 km with isotopically heavy iron (δ56Fe = 0.79 to 0.90‰) and unradiogenic osmium (187Os/188Os = 0.111). These iron values lie outside the range of known mantle compositions or expected reaction products at depth. This signature represents subducted iron from magnetite and/or Fe-Ni alloys precipitated during serpentinization of oceanic peridotite, a lithology known to carry unradiogenic osmium inherited from prior convection and melt depletion. These diamond-hosted inclusions trace serpentinite subduction into the mantle transition zone. We propose that iron-rich phases from serpentinite contribute a labile heavy iron component to the heterogeneous convecting mantle eventually sampled by oceanic basalts. |
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