Rare earth elements and neodymium isotopes in the South Pacific: impact of hydrothermal activity, particle fluxes, and ocean circulation

了解海洋中影响微量元素及其同位素（TEI）的地球化学过程及其对TEI分布和预算的影响，对于全面了解TEI作为微量营养素和示踪剂的作用至关重要。钕（Nd）同位素和稀土元素（REE）是非常有用的海洋示踪剂，已被广泛应用于提高我们对现代和过去海洋过程和变化的认识。稀土元素的颗粒反应性和Nd同位素所携带的源信息使它们特别适用于阐明溶解的TEI源和海洋中的修改，颗粒清除和水团的横向运输。在这里提出的研究中，我将测试的假设，热液颗粒导致强烈的稀土元素清除和特征稀土元素和Nd同位素的签名，使跟踪的命运热液羽在南太平洋和潜在的上涌到南大洋的表面。此外，我将测试是否在贫营养亚热带南太平洋环流的极低的颗粒通量导致横向平流在这一地区的溶解稀土元素的分布占主导地位的控制。该项目将进一步评估新形成的南大洋水团的原始溶解Nd同位素特征可能因新西兰的输入和/或与新西兰边缘和Kermadec热液系统的接触而发生的变化。因此，这项研究将深入了解南东太平洋隆起高度活跃的热液系统的影响，以及迄今为止在很大程度上未研究的Kermadec弧溶解稀土和Nd同位素的浅和相对于TEIs的热液系统在太平洋。预期的结果将有深远的影响，全球稀土在海洋中的预算，使用稀土和Nd同位素作为示踪剂，以及其他溶解TEIs的研究过程的影响。

Knowledge of the biogeochemical processes affecting trace elements and their isotopes (TEIs) in the ocean and their impact on TEI distributions and budgets is essential for a comprehensive understanding of the roles of TEIs as micronutrients and tracers. Neodymium (Nd) isotopes and rare earth elements (REEs) are highly useful marine tracers and have been widely applied to improve our understanding of both modern and past processes and changes in the ocean. The particle reactivity of REEs and the source information carried by Nd isotopes make them particularly useful for elucidating dissolved TEI sources and modifications in the ocean, scavenging by particles, and lateral transport by water masses. In the study proposed here, I will test the hypotheses that hydrothermal particles lead to intense REE scavenging and characteristic REE and Nd isotope signatures that allow tracing the fate of hydrothermal plumes in the South Pacific and potentially their upwelling to the surface of the Southern Ocean. Moreover, I will test whether the extremely low particle fluxes in the oligotrophic subtropical South Pacific gyre lead to a dominant control of lateral advection on the distribution of dissolved REEs in this area. The project will further assess the potential modification of the original dissolved Nd isotope signatures of newly formed Southern Ocean water masses through input from New Zealand and/or contact with the New Zealand margin and the Kermadec hydrothermal system. The study will therefore provide insight into the impact of the highly active hydrothermal system of the southern East Pacific Rise, as well as the shallow and with respect to TEIs so far largely unstudied hydrothermal system of the Kermadec Arc on dissolved REEs and Nd isotopes in the Pacific. The expected results will have far-reaching implications for the global REE budget in the ocean, the use of REEs and Nd isotopes as tracers, as well as for the impact of the studied processes on other dissolved TEIs.