Bioapatite is widely recognized as the primary carrier for rare earth elements and yttrium (REY) in deep-sea REY-rich muds. The incorporation of REY into bioapatite occurs at the water-sediment interface, which has the potential to serve as a proxy for reconstructing paleoenvironmental conditions. The timing of REY uptake and the fractionation of rare earth elements (REEs) within bioapatite are crucial factors to understanding the application of these proxies. In this study, we present in-situ geochemical data for bioapatite obtained from surface sediments in the high sedimentation rate Somali Basin of the northwestern Indian Ocean (NWIO), as well as fish teeth within nodules from the low sedimentation rate in the northwestern Pacific Ocean (NWPO). Our findings indicate that the uptake time of REY occurred rapidly, with the ΣREY content reaching 7265 μg/g in bioapatite from the surface sediments in the NWIO within several thousand years. The bone fragments exhibited a high ΣREY content, which was primarily attributed to substitution processes. This led to a notably elevated proportion of middle rare earth elements (MREE) compared to fish teeth. In contrast, the adsorption and substitution mechanisms responsible for REY incorporation decreased from the root to the tip in fish teeth, resulting in a pronounced decline in ΣREY content. The adsorption mechanism was identified as the primary process responsible for REY uptake in the fish teeth within the studied nodules from the NWPO. The fractionation pattern of REEs in these teeth exhibited similarities to that of fish teeth from the NWIO. Therefore, we inferred that the fish teeth within the studied nodules may preserve the original information during late diagenesis. The variation of REY contents in the nodules was influenced by the redox environment, and there is no evidence to support the migration of REY from the nodules into the fish teeth.

中文翻译：

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深海生物磷灰石中稀土元素的吸收时间及富集机制


生物磷灰石被广泛认为是深海富含 REY 的泥浆中稀土元素和钇 (REY) 的主要载体。 REY 与生物磷灰石的结合发生在水-沉积物界面，这有可能作为重建古环境条件的代理。 REY 吸收的时间和生物磷灰石中稀土元素 (REE) 的分馏是了解这些替代物应用的关键因素。在这项研究中，我们提供了从西北印度洋（NWIO）高沉积速率索马里海盆的表层沉积物中获得的生物磷灰石的原位地球化学数据，以及从西北太平洋低沉积速率的结核内鱼牙的数据（NWPO）。我们的研究结果表明，REY 的吸收时间发生得很快，在几千年内，NWIO 表面沉积物中生物磷灰石中的ΣREY 含量达到了 7265 μg/g。骨碎片表现出较高的 ΣREY 含量，这主要归因于替代过程。与鱼牙相比，这导致中稀土元素（MREE）的比例显着升高。相比之下，鱼牙中负责REY掺入的吸附和取代机制从根部到尖端逐渐减少，导致ΣREY含量显着下降。吸附机制被认为是 NWPO 结核中鱼牙吸收 REY 的主要过程。这些牙齿中稀土元素的分馏模式与 NWIO 的鱼牙相似。因此，我们推断所研究的结核内的鱼齿可能保留了晚期成岩作用的原始信息。 结核中REY含量的变化受到氧化还原环境的影响，没有证据支持REY从结核迁移到鱼牙中。