近日，美国劳伦斯·利弗莫尔国家实验室Gregory A. Brennecka团队研究了锌同位素对百慕大地幔源区碳循环的约束。2025年9月15日出版的《地质学》杂志发表了这项成果。

地幔过渡带（MTZ）挥发物的再循环和储存对上地幔的再利用具有重要意义，并与高μ (HIMU) （μ为²³⁸U/²⁰⁴Pb）地幔的生成有关。探测MTZ和与地幔对流相关过程的一种方法是取样来自浅层地幔并被MTZ上升流污染的熔岩，如先前提出的百慕大浅层羽流。

研究组首次测定了百慕大硅质欠饱和和硅质饱和熔岩的δ⁶⁶Zn同位素组成，以探讨北大西洋西部富碳岩性的成因和大型海山的成因。与全球δ⁶⁶Zn数据对比，δ⁶⁶Zn在0.24±0.04 ~ 0.41±0.04之间，不支持对百慕大HIMU地幔中再生海相碳酸盐的直接采样。相反，研究组认为δ⁶⁶Zn向高值分馏与岩浆过程和碳酸盐形成相关的深部流体中碳的掺入有关。这些富含碳的流体很可能是由亚佩特海岩石圈俯冲冷板块之间的交代反应形成的。500 Ma与盘古大陆岩石圈地幔增厚的关系。晚新生代法拉龙板块通过浅层对流到达北美东部边缘，引发了这一交代地幔的融化。

附：英文原文

Title: Zinc isotope constraints on the cycling of carbon in the Bermuda mantle source

Author: Sarah E. Mazza, Jan Render, Caroline Ruppert, Steven B. Shirey, Josh Wimpenny, Gregory A. Brennecka

Issue&Volume: 2025-09-15

Abstract: Volatile recycling and storage in the mantle transition zone (MTZ) is important for the refertilization of the upper mantle and is associated with the generation of high-μ (HIMU, where μ is 238U/204Pb) mantle. One way to probe the MTZ and the processes associated with mantle convection is to sample lavas that originate from the shallow mantle and were contaminated by upwelling from the MTZ, such as at the previously proposed shallow plume of Bermuda. Here we present the first δ66Zn isotopic compositions of Bermuda silica-undersaturated and silica-saturated lavas to explore the origin of the carbon-rich lithologies and the genesis of the large seamount found in the western North Atlantic Ocean. Contrasting with global δ66Zn data sets, our results (δ66Zn between 0.24 ± 0.04 and 0.41 ± 0.04) do not support direct sampling of recycled marine carbonates in the Bermuda HIMU mantle. Instead, we show that δ66Zn fractionation toward higher values is associated with magmatic processes and incorporation of carbon sourced from deep fluids associated with the formation of carbonatites. These carbon-rich fluids are likely sourced from the metasomatic reactions between the subducted cold slab of the Iapetus oceanic lithosphere ca. 500 Ma and the thickened continental lithospheric mantle of Pangea. Melting of this metasomatized mantle was triggered by the arrival of the Farallon slab to the eastern North American margin in the late Cenozoic via shallow convection.

DOI: 10.1130/G53656.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G53656.1/661230/Zinc-isotope-constraints-on-the-cycling-of-carbon