The Mercury Isotopic Composition of Earth's Mantle and the Use of Mass Independently Fractionated Hg to Test for Recycled Crust

The element mercury (Hg) can develop large mass-independent fractionation (MIF) (Δ199Hg) due to photo-chemical reactions at Earth's surface. This results in globally negative Δ199Hg for terrestrial sub-aerially-derived materials and positive sub-aqueously-derived marine sediments. mantle composition least affected by crustal recycling is estimated from high-3He/4He lavas Samoa Iceland, providing an average of = 0.00 ± 0.10, Δ201Hg −0.02 0.0.09, δ202Hg −1.7 1.2; 2SD, N 11. By comparison, a HIMU-type lava Tubuai exhibits Δ199Hg, consistent with altered oceanic crust its source. A Samoan (EM2) has reflecting incorporation continental into Three Pitcairn exhibit which correlate 87Sr/86Sr, variable proportions (low high 87Sr/86Sr) (high low material their sources. These observations indicate that MIF signatures offer powerful tool examining atmosphere-deep Earth interactions.