Origin of geochemical mantle components: Role of subduction filter
Origin of geochemical mantle components: Role of subduction filter
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DOI：
10.1002/2016gc006343
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发表时间：
2016-08
期刊：
影响因子：
3.7
通讯作者：
J. Kimura;J. Gill;S. Skora;P. V. van Keken;H. Kawabata
中科院分区：
文献类型：
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作者：
J. Kimura;J. Gill;S. Skora;P. V. van Keken;H. Kawabata
我们定量探索元素再分配在俯冲带使用数值质量平衡模型，以评估俯冲带过滤器在地球地球化学循环中的作用。我们的模型弧岩浆成因后的板块残留物不同于以前的内部一致的现代弧，成功地解释弧岩浆成因的地球动力学模型，包括每个底层板组件的脱水/熔融的元素通量。我们假设地幔位温（Tp）在3.5-1.7 Ga时为1400-1650°C，并逐渐降低到今天的1300-1350°C。温压为1650°C的热俯冲带具有类似于现代日本西南部的热结构，在那里形成了高镁安山岩，其化学性质类似于大陆地壳。热俯冲带残留的火成岩洋壳在地幔中储存2.5-1.7 Gyr后，可同位素演化为HIMU地幔组分，地幔楔残留的基底演化为EMI，残留的沉积物成为EMII的重要组成部分，地幔楔残留的顶部可演化为陆下岩石圈组分。共同带或焦点带成分是前三个残留物的稳定混合物，偶尔与早期亏损地幔混合。较早回收的板状残留物（约2.5 Ga）在南半球形成DUPAL异常，而最近回收的残留物（约1.7 Ga）位于北方半球。这些年龄对应于主要的大陆地壳形成事件。亏损上地幔的东西向不均匀性除太平洋外还包括陆下地幔。
We quantitatively explore element redistribution at subduction zones using numerical mass balance models to evaluate the roles of the subduction zone filter in the Earth's geochemical cycle. Our models of slab residues after arc magma genesis differ from previous ones by being internally consistent with geodynamic models of modern arcs that successfully explain arc magma genesis and include element fluxes from the dehydration/melting of each underlying slab component. We assume that the mantle potential temperature (Tp) was 1400–1650°C at 3.5–1.7 Ga and gradually decreased to 1300–1350°C today. Hot subduction zones with Tp ∼1650°C have a thermal structure like modern SW Japan where high‐Mg andesite is formed which is chemically like continental crust. After 2.5–1.7 Gyr of storage in the mantle, the residual igneous oceanic crust from hot subduction zones can evolve isotopically to the HIMU mantle component, the residual base of the mantle wedge to EMI, the residual sediment becomes an essential part of EMII, and the residual top of the mantle wedge can become the subcontinental lithosphere component. The Common or Focal Zone component is a stable mixture of the first three residues occasionally mixed with early depleted mantle. Slab residues that recycled earlier (∼2.5 Ga) form the DUPAL anomaly in the southern hemisphere, whereas residues of more recent recycling (∼1.7 Ga) underlie the northern hemisphere. These ages correspond to major continental crust forming events. The east‐west heterogeneity of the depleted upper mantle involves subcontinental mantle except in the Pacific.