We report on the abundances of REE in a comprehensive suite of shells of deep-sea chemosynthetic mussels from hydrothermal vents and cold seeps. Except for mussel shells from oceanic hydrothermal sites that often show extremely pronounced Eu anomalies ((Eu/Sm)_sn = 2–200), and abundances for this element that can occasionally exceed 200 ng/g, REE concentrations are usually low and typically between 10⁻⁴ and 10⁻³ times the shale reference.

In addition to exhibiting commonly high Eu anomalies, mussel shells from hydrothermal vents are depleted in light-REE and heavy-REE compared to reference shales (e.g., Pr/Sm)_sn < 1, (Tb/Yb)_sn = 1–6). These features are inherited from hydrothermal fluid. Mussel shells from cold seeps have very different REE concentrations, which also reflect the compositions of the waters they filter: their (Eu/Sm)_sn ratios are much lower (<2) and are much less heavy-REE fractionated ((Tb/Yb)_sn = 0.5–2.7). Furthermore, the REE distributions show a clear dichotomy between thiotrophic and methanotrophic mussels. The latter show marked enrichments in light-REE and even sometimes La enrichments much larger than those classically observed in deep-sea waters, leading to huge positive La anomalies (La/La* > 10). These light-REE enrichments are likely related to REE-dependent methanol dehydrogenase enzymes used by the symbionts that these mussels host in their gills. These data show that REE chemistry is a promising tool to study chemosynthetic faunas living near hydrothermal vents or cold seeps. Furthermore, REE chemistry, coupled with stable isotopes, should reveal the footprint of aerobic methanotrophy in carbonates formed in cold seeps, but also potentially in ancient sediments.

我们报告了来自热液喷口和冷泉的一整套深海化学合成贻贝壳中 REE 的丰度。除了来自海洋热液地点的贻贝壳经常表现出极其明显的 Eu 异常（（Eu/Sm）_sn  = 2-200），并且该元素的丰度偶尔会超过 200 ng/g，REE 浓度通常很低，通常介于页岩参考值的10 ^-4和 10 ^-3倍。

除了表现出普遍的高 Eu 异常外，与参考页岩相比，来自热液喷口的贻贝壳在轻稀土元素和重稀土元素中耗尽（例如，Pr/Sm）_sn  < 1，（Tb/Yb）_sn  = 1-6） . 这些特征继承自热液流体。来自冷泉的贻贝壳具有非常不同的 REE 浓度，这也反映了它们过滤的水的成分：它们的 (Eu/Sm)_锡比低得多 (<2) 并且重稀土分馏的程度要低得多 ((Tb/Yb )_锡 = 0.5–2.7)。此外，REE 分布显示出硫营养型和甲烷营养型贻贝之间的明显二分法。后者在轻稀土元素中显示出明显的富集，甚至有时 La 富集比在深海水域中经典观察到的大得多，导致巨大的正 La 异常（La/La* > 10）。这些轻稀土元素的富集可能与这些贻贝在其鳃中宿主的共生体使用的依赖稀土元素的甲醇脱氢酶有关。这些数据表明，稀土元素化学是研究生活在热液喷口或冷泉附近的化学合成动物群的有前途的工具。此外，稀土元素化学与稳定同位素相结合，应该可以揭示冷泉中形成的碳酸盐中好氧甲烷氧化的足迹，但也可能存在于古代沉积物中。