Radiogenic and Stable Isotope Evidence for Recycling of Ancient Oceanic Crust in High-Nb Basalts From Baja California, Mexico

IF 4.6 1区地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Geophysical Research Letters Pub Date : 2025-09-19 DOI:10.1029/2025GL115035

Hai-Quan Liu, Jie Li, Thierry Calmus, Alfredo Aguillón-Robles, Le Zhang, Long Zhang, Xiao-Long Huang, Yi-Gang Xu

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Abstract

The genesis of high-Nb basalts (HNB) in subduction zones remains controversial, attributed to melting products of metasomatized mantle linked to recent or ancient subduction events. Here we present radiogenic isotope and molybdenum compositions for post-subduction HNBs and adakites from Baja California, Mexico. The HNBs show more radiogenic Sr-Pb and less unradiogenic Nd-Hf isotopes compared to the adakites. Their Mo isotopic enrichment (δ^98/95Mo), up to −0.12‰ relative to the depleted mantle (−0.21‰), is linked to FOZO (Focal Zone)-like Sr-Nd-Hf-Pb isotopic signatures. These features indicate compositional contribution of recycled, ancient oceanic crust (>1 Gyr), carrying heavy Mo under reduced conditions through serpentinite-related interactions and losing varying amounts of Rb, Nd, Hf, and Pb relative to bulk oceanic crust during subduction dehydration. Our new data reveal ancient contributions to HNB formation and underscore the role of subducted oceanic crust and serpentinite to the formation of FOZO mantle signatures.

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墨西哥下加利福尼亚高铌玄武岩古洋壳再循环的放射性成因和稳定同位素证据

俯冲带高铌玄武岩（HNB）的成因仍有争议，其成因与近代或古代俯冲事件有关。本文报道了墨西哥下加利福尼亚地区俯冲后HNBs和埃达克岩的放射性成因同位素和钼组成。与埃达克岩相比，HNBs显示出更多的放射性Sr-Pb和更少的非放射性Nd-Hf同位素。Mo同位素富集（δ98/95Mo），相对于贫地幔（- 0.21‰）高达- 0.12‰，与FOZO （Focal Zone）型Sr-Nd-Hf-Pb同位素特征有关。这些特征表明，古海洋地壳（>1 Gyr）的成分贡献，通过与蛇纹岩相关的相互作用，在还原条件下携带重Mo，并在俯冲脱水过程中相对于大块海洋地壳损失不同数量的Rb、Nd、Hf和Pb。我们的新数据揭示了HNB形成的古代贡献，并强调了俯冲洋壳和蛇纹岩对FOZO地幔特征形成的作用。

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来源期刊

Geophysical Research Letters 地学-地球科学综合

CiteScore

9.00

自引率

9.60%

发文量

1588

审稿时长

2.2 months

期刊介绍： Geophysical Research Letters (GRL) publishes high-impact, innovative, and timely research on major scientific advances in all the major geoscience disciplines. Papers are communications-length articles and should have broad and immediate implications in their discipline or across the geosciences. GRLmaintains the fastest turn-around of all high-impact publications in the geosciences and works closely with authors to ensure broad visibility of top papers.