Mechanisms of trace-metal incorporation in ferromanganese deposits: implications for reconstructing ocean history

铁锰矿床中痕量金属的掺入机制：对重建海洋历史的影响

• 批准号: NE/F00043X/1
• 负责人: Caroline Peacock
• 金额: $ 6.64万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FF00043X%2F1
• 关键词: Mechanisms; trace; metal; incorporation; ferromanganese

Ferromanganese (FeMn) nodules were first discovered during the Challenger expedition over 130 years ago. Since then, nodules and encrustations have been found in abundance throughout the world's oceans. Nodules (on the seafloor) and crusts (on exposed rock outcrops) are predominantly formed of interlaminated iron (Fe) and manganese (Mn) minerals precipitated from seawater over millions of years. These minerals are extremely efficient scavengers of trace-metals from seawater and, as such, FeMn deposits are enriched in trace-metals, often at economically valuable levels. In addition to their economic value, scientists currently use FeMn deposits to reconstruct aspects of ocean history. Scientists might also, however, be able to use these deposits to provide more detailed information about past ocean conditions by measuring variations in the concentrations of the scavenged trace-metals. For example, vanadium (V) is a trace-metal that exists in different states depending on the level of oxygen in the surrounding seawater. If deposits are found that contain V in a reduced state, scientists can infer that at this point in the deposit's history the seawater that sourced the V was low in oxygen - suboxic - or completely without oxygen - anoxic. This in turn has implications for the oceanic cycling of trace-metals between biotic (biological) and abiotic (geological) compartments and, for example, for the extent of oceanic vertical mixing. However, in order to reliably reconstruct past ocean conditions, the V seawater signature, recording V in a reduced state, must be unaltered since the original V incorporation. Scientists must be sure, therefore, that V is permanently locked-in to FeMn deposits when it is scavenged, i.e., it is essential to know how V is incorporated. Advanced spectroscopic techniques - using synchrotron light - can reveal the different states (like reduced V) and the coordination environment of a trace-metal in a FeMn deposit. In doing so, these techniques reveal how trace-metals are incorporated in FeMn deposits. Certain mechanisms of incorporation are reversible, while others are irreversible. A trace-metal incorporated in FeMn nodules via an irreversible mechanism will be permanently locked into the nodules and, as such, these deposits will have faithfully recorded original seawater signatures of that trace-metal. Despite a vast number of scientific investigations into FeMn deposits, advanced spectroscopic techniques have never been used to reveal how a range of trace-metals (useful for reconstructing past ocean conditions) are incorporated. As such, scientists have only an empirical understanding of trace-metal incorporation i.e., they know that a particular trace-metal is enriched in a particular type of deposit and they know whether the trace-metal is found associated with the Fe-rich or Mn-rich phase, but it is unclear how this enrichment has occurred and why certain trace-metals prefer Fe- or Mn-rich minerals. This current level of understanding is not adequate to establish whether seawater trace-metal signatures are permanently recorded. As such, we are potentially missing out on a wealth of detailed information about past ocean conditions that cannot be ascertained by other means. This work will use advanced spectroscopic techniques to reveal how 5 geochemically important trace-metals are incorporated in the full range of FeMn deposits. This will be the first coordinated study designed to reveal whether trace-metals are permanently scavenged into these deposits and, as such, will provide fundamental new information on trace-metal incorporation in natural FeMn deposits. Moreover, the proposed work will open the possibility that FeMn deposits can be used to provide a wealth of new information about both local and global ocean history.

铁锰结核是130多年前“挑战者”号考察期间首次发现的。自那时以来，在世界各大洋发现了大量结核和结壳。结核（在海底）和结壳（在裸露的岩石露头上）主要由数百万年来从海水中沉淀出来的层间铁（Fe）和锰（Mn）矿物形成。这些矿物是海水中痕量金属的极有效的清除剂，因此，FeMn矿床富含痕量金属，通常处于具有经济价值的水平。除了经济价值外，科学家目前还利用铁锰矿床重建海洋历史的各个方面。然而，科学家们也可以利用这些沉积物，通过测量被清除的微量金属浓度的变化，提供有关过去海洋状况的更详细信息。例如，钒（V）是一种微量金属，根据周围海水中的氧气水平，以不同的状态存在。如果发现沉积物中含有还原态的钒，科学家可以推断，在存款历史的这一点上，来源于钒的海水是低氧的--或者完全没有氧--缺氧。这反过来又影响到微量金属在生物（生物）和非生物（地质）区室之间的海洋循环，例如影响到海洋垂直混合的程度。然而，为了可靠地重建过去的海洋条件，V海水签名，记录在还原状态的V，必须是不变的，因为原来的V掺入。因此，科学家们必须确定，当钒被清除时，它会永久地锁定在锰铁矿床中，即，必须知道V是如何结合的。先进的光谱技术-使用同步加速器光-可以揭示FeMn存款中痕量金属的不同状态（如还原V）和配位环境。在这样做的过程中，这些技术揭示了微量金属是如何被纳入锰铁矿床。某些结合机制是可逆的，而另一些是不可逆的。铁锰结核中的微量金属通过不可逆机制被永久锁定在结核中，因此，这些矿床将忠实地记录该微量金属的原始海水特征。尽管对FeMn矿床进行了大量的科学调查，但先进的光谱技术从未被用于揭示一系列痕量金属（用于重建过去的海洋条件）是如何被纳入的。因此，科学家对痕量金属的掺入只有经验性的理解，即，他们知道特定的微量金属在特定类型的存款中富集，并且他们知道微量金属是否与富Fe或富Mn相相关联，但是不清楚这种富集是如何发生的，以及为什么某些微量金属更喜欢富Fe或富Mn的矿物。目前的理解水平不足以确定海水微量金属特征是否被永久记录。因此，我们可能错过了大量关于过去海洋状况的详细信息，这些信息无法通过其他手段确定。这项工作将使用先进的光谱技术，以揭示如何5地球化学重要的微量金属纳入全方位的FeMn矿床。这将是第一个协调的研究，旨在揭示微量金属是否被永久清除到这些矿床，因此，将提供有关微量金属纳入天然FeMn矿床的基本新信息。此外，拟议的工作将打开的可能性，铁锰矿床可用于提供丰富的新信息，当地和全球的海洋历史。

项目成果

Oxidative scavenging of thallium by birnessite: explanation for thallium enrichment and stable isotope fractionation in marine ferromanganese precipitates

• DOI: 10.1016/j.gca.2012.01.036
• 发表时间: 2012-05
• 期刊: Geochimica et Cosmochimica Acta
• 影响因子: 5
• 作者: C. Peacock;E. Moon

Limited Zn and Ni mobility during simulated iron formation diagenesis

模拟铁形成岩作用过程中锌和镍的流动性有限

• DOI: 10.1016/j.chemgeo.2015.02.037
• 发表时间: 2015
• 期刊: Chemical Geology
• 影响因子: 3.9
• 作者: Robbins L

Adsorption of Cu(II) to ferrihydrite and ferrihydrite-bacteria composites: Importance of the carboxyl group for Cu mobility in natural environments

• DOI: 10.1016/j.gca.2012.06.012
• 发表时间: 2012-09-01
• 期刊: GEOCHIMICA ET COSMOCHIMICA ACTA
• 影响因子: 5
• 作者: Moon, Ellen M.;Peacock, Caroline L.
• 通讯作者: Peacock, Caroline L.