资源环境科技发展态势分析平台

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