Rare Earth Elements and Nd Isotopes in Hydrothermal Metalliferous Sediments: Pleistocene and Cenozoic Paleoceanography

在这项研究中，PI将测试和开发一种新的古气候指标--碳酸盐沉积物中稀土元素(REE)的丰度，其中包含源自热液羽流的金属沉积物。结合起来，PI将使用ND同位素值(？ND)作为替代，以帮助揭示风化速率的差异和由于其他原因导致的海水REE丰度变化的来源。稀土元素的短停留时间(1-4kA)意味着这些替代物有可能提供高分辨率数据。初步数据表明，金属沉积物记录了底水稀土元素模式，而大西洋和太平洋的稀土元素模式实际上是相同的。整个稀土配分模式反映在Nd/Er的差异上。近135kA岩心的初步数据表明，Nd/Er和？O具有很好的相关性，显示出良好的替代潜力。更长时期(最后28 Ma)的其他初步数据显示，这一时期的ND和ND/ER具有有趣的模式和较大的变化，再次证明这些联合指标有可能识别海洋风化输入的变化。为了进一步评估这一代理，PIS将分析来自EPR北部和南部额外热液喷口的热液羽流物质，进行体外REE吸收的实验室实验，利用全新世岩芯顶部标定NdEr代理，利用具有已知和不同成岩历史的岩芯评估可能的成岩作用对代理信号保存的影响，并探索这两种代理在Ma至10kA时间尺度上在渐新世和中新世气候变化较大的情况下的行为。

In this study, the PIs will test and develop a new paleoclimate proxy- Rare Earth Element (REE) abundances of carbonate sediments that contain metalliferous sediment originating from hydrothermal plumes. In combination, the PIs will use Nd isotope values (?Nd) as a proxy to help unravel differences in weathering rates and sources from variations in seawater REE abundances due to other causes. The short residence times of the REE (1-4 Ka) mean that potentially, these proxies could provide high resolution data. Preliminary data show that metalliferous sediment records bottom water REE patterns and that the REE patterns are virtually identical for the Atlantic and Pacific. The entire REE pattern is reflected in differences in Nd/Er. Preliminary data for a core for the last 135 Ka indicate that Nd/Er and ???O are well correlated, showing good potential for the proxy. Additional preliminary data for a longer period (last 28Ma) show interesting patterns and large changes in ?Nd and Nd/Er for this period, again arguing that these combined proxies have potential to identify changing weathering inputs to the ocean. In order to further evaluate this proxy, the PIs will analyze hydrothermal plume material from additional hydrothermal vents in the northern and southern EPR, carry out lab experiments of REE uptake in vitro, calibrate the Nd/Er proxy using Holocene core tops from SEPR cores, evaluate possible diagenetic effects on the preservation of the proxy signals using cores with known and diverse diagenetic histories, and explore the behavior of both proxies on Ma to 10 Ka time scales for large climatic variations in the Oligocene and Miocene.