Recycled Components in Mantle Plumes Deduced From Variations in Halogens (Cl, Br, and I), Trace Elements, and 3 He/ 4 He Along the Hawaiian‐Emperor Seamount Chain
Recycled Components in Mantle Plumes Deduced From Variations in Halogens (Cl, Br, and I), Trace Elements, and 3 He/ 4 He Along the Hawaiian‐Emperor Seamount Chain
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夏威夷海山链沿线的卤素（Cl、Br 和 I）、微量元素和 3 He/ 4 He 变化推断地幔羽流中的回收成分
DOI：
10.1029/2018gc007959
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Ballentine, Chris J.
中科院分区：
文献类型：
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作者：
Broadley, Michael W.;Sumino, Hirochika;Graham, David W.;Burgess, Ray;Ballentine, Chris J.
卤素主要位于地球表面的储藏层内；因此，它们已被证明是识别地幔内俯冲挥发物的有效示踪剂。俯冲岩性表现出各种各样的卤素成分，但地幔保持着相当一致的特征，这表明在俯冲到地幔或喷发期间，卤素可能是均一化的。在这里，我们提供了沿夏威夷-帝王海山链的三座海山的卤素(氯、溴和碘)、钾、惰性气体以及橄榄石的常量和微量元素数据，以确定深部地幔来源是否保留了通过俯冲引入的卤素不均一性的证据。高镍含量表明夏威夷-帝王地幔源区含有辉石岩形式的再循环洋壳成分，从最古老的(底特律)的46%增加到年轻的海山(科科)的70%。底特律海山保留了类似大洋中脊玄武岩(MORB)的BR/Cl值和I/Cl值，而Suiko和Koko海山的BR/Cl值和I/Cl值高于MORB，类似于蚀变洋壳和脱水蛇纹岩。氦同位素显示出类似的演化，从底特律海山的类似MORB的值到Suiko和Koko海山的更高值。辉石岩贡献、溴/氯、I/氯和~3He/~4He之间的相关性表明，俯冲物质已并入原始未脱气夏威夷地幔热柱来源。微量元素和卤素中循环洋壳特征的识别表明，蚀变洋壳的俯冲和脱水作用可能对挥发性元素向深部地幔的循环起到控制作用。
Halogens are primarily located within surface reservoirs of the Earth; as such they have proven to be effective tracers for the identification of subducted volatiles within the mantle. Subducting lithologies exhibit a wide variety of halogen compositions, yet the mantle maintains a fairly uniform signature, suggesting halogens may be homogenized during subduction to the mantle or during eruption. Here we present halogen (Cl, Br, and I), K, noble gas, and major and trace element data on olivines from three seamounts along the Hawaiian‐Emperor seamount chain to determine if the deep mantle source has retained evidence of halogen heterogeneities introduced through subduction. High Ni contents indicate that the Hawaiian‐Emperor mantle source contains a recycled oceanic crust component in the form of pyroxenite, which increases from the 46% in the oldest (Detroit) to 70% in the younger seamount (Koko). Detroit seamount retains mid‐ocean ridge basalts (MORB)‐like Br/Cl and I/Cl, while the Br/Cl and I/Cl of Suiko and Koko seamounts are higher than MORB and similar to altered oceanic crust and dehydrated serpentinite. Helium isotopes show a similar evolution, from MORB‐like values at Detroit seamount toward higher values at Suiko and Koko seamounts. The correlation between pyroxenite contributions, Br/Cl, I/Cl, and3He/4He indicates that subducted material has been incorporated into the primordial undegassed Hawaiian mantle plume source. The identification of recycled oceanic crustal signatures in both the trace elements and halogens indicates that subduction and dehydration of altered oceanic crust may exert control on the cycling of volatile elements to the deep mantle.