The Mercury Isotopic Composition of Earth's Mantle and the Use of Mass Independently Fractionated Hg to Test for Recycled Crust
The Mercury Isotopic Composition of Earth's Mantle and the Use of Mass Independently Fractionated Hg to Test for Recycled Crust
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DOI：
10.1029/2021gl094301
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发表时间：
2021-09-16
影响因子：
5.2
通讯作者：
Chen, Jiubin
中科院分区：
文献类型：
--
作者：
Moynier, Frederic;Jackson, Matthew G.;Chen, Jiubin
由于地球表面的光化学反应，元素汞(Hg)可以产生大的质量无关分馏(MIF)(增量Hg-199)。这导致全球陆地次空中衍生物质的增量汞-199为负，而次水面衍生海洋沉积物的增量汞-199为正。受地壳再循环影响最小的地幔成分来自萨摩亚和冰岛的高He-3/He-4熔岩，其平均值为Delta Hg-199=0.00+/-0.10，Delta Hg-201=-0.02+/-0.0.09，Delta Hg-202=-1.7+/-1.2；2SD，N=11。相比之下，来自图布艾的HIMU型熔岩呈现正的Delta Hg-199，与其地幔源区的洋壳蚀变一致。萨摩亚(EM2)熔岩具有负的Hg-199增量，反映了陆壳物质并入其源区。3个皮特凯恩熔岩显示正的Hg199增量，与其地幔来源中陆相物质(低Hg199和高Sr-87/Sr-86)和洋壳物质(高Hg199和低Sr-87/Sr86)的不同比例一致。这些观测表明，MIF信号为研究大气-地球深层相互作用提供了一个强大的工具。
The element mercury (Hg) can develop large mass-independent fractionation (MIF) (Delta Hg-199) due to photo-chemical reactions at Earth's surface. This results in globally negative Delta Hg-199 for terrestrial sub-aerially-derived materials and positive Delta Hg-199 for sub-aqueously-derived marine sediments. The mantle composition least affected by crustal recycling is estimated from high-He-3/He-4 lavas from Samoa and Iceland, providing an average of Delta Hg-199 = 0.00 +/- 0.10, Delta Hg-201 = -0.02 +/- 0.0.09, delta Hg-202 = -1.7 +/- 1.2; 2SD, N = 11. By comparison, a HIMU-type lava from Tubuai exhibits positive Delta Hg-199, consistent with altered oceanic crust in its mantle source. A Samoan (EM2) lava has negative Delta Hg-199 reflecting incorporation of continental crust materials into its source. Three Pitcairn lavas exhibit positive Delta Hg-199 which correlate with Sr-87/Sr-86, consistent with variable proportions of continental (low Delta Hg-199 and high Sr-87/Sr-86) and oceanic (high Delta Hg-199 and low Sr-87/Sr-86) crustal material in their mantle sources. These observations indicate that MIF signatures offer a powerful tool for examining atmosphere-deep Earth interactions.