Abstract It has been hypothesized that vanadium (V) isotopes have the potential to track sedimentary redox conditions due to multiple valence states occurring in nature, which might induce variable V isotope fractionation as a function of sedimentary redox state. These characteristica could make V isotopes a useful paleo-redox proxy. However, in order to understand the mechanisms driving V isotope fractionation, it is crucial to build a framework for the depositional and post-depositional controls on sedimentary V isotope records from a diverse set of sedimentary environments. This study, for the first time, investigates the V isotope variations of modern marine sediments deposited under a range of redox environments. Our results document that changes in local redox conditions impart a significant isotopic fractionation from seawater as recorded in the local sedimentary V isotopic signature. Importantly, there is a significant difference between the V isotope composition of sediments deposited in the open ocean setting with oxygen-deficient bottom waters compared to less reducing environments, whereby oxic sediments (benthic oxygen contents > 10 μΜ) exhibit Δoxic = −1.1 ± 0.3‰ and anoxic sediments exhibit Δanoxic = −0.7 ± 0.2‰. Combined with previous studies on seawater particulate and sediment pore fluid analysis, our results indicate that V is mainly delivered and enriched in anoxic sediments through settling particulates. Authigenic V isotope compositions in marine sediments are likely controlled by isotope fractionation between V species bound to particulates and dissolved in seawater, which likely varies with the speciation and adsorption properties of V that are strongly controlled by local redox conditions. In addition, the euxinic Cariaco Basin sediments exhibit distinctive Δeuxinic = −0.4 ± 0.2‰, which is likely influenced by the relationship between the seawater V removal rate and the seawater renewal rate. Our results highlight the direct link between authigenic marine sedimentary V isotope compositions and the overlying local redox conditions. This investigation of V isotopes in modern marine environments provides an initial framework for the utilization of V isotopes to reconstruct ancient redox fluctuations, which has the potential to track subtle redox variations of local oxygen-deficient to low oxygen environments.

中文翻译：

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低氧海洋条件下的沉积钒同位素特征

摘要 已经假设钒 (V) 同位素具有跟踪沉积氧化还原条件的潜力，因为自然界中存在多种价态，这可能会导致可变的 V 同位素分馏作为沉积氧化还原状态的函数。这些特征可以使 V 同位素成为有用的古氧化还原代理。然而，为了理解驱动 V 同位素分馏的机制，至关重要的是为来自不同沉积环境的沉积 V 同位素记录建立一个沉积和沉积后控制框架。这项研究首次调查了沉积在一系列氧化还原环境下的现代海洋沉积物的 V 同位素变化。我们的结果证明，局部氧化还原条件的变化会导致海水中显着的同位素分馏，如当地沉积 V 同位素特征中所记录。重要的是，与还原性较低的环境相比，沉积在缺氧底水的开阔海洋环境中沉积物的 V 同位素组成存在显着差异，其中含氧沉积物（底栖氧含量 > 10 μM）表现出 Δoxic = -1.1 ± 0.3 ‰ 和缺氧沉积物表现出 Δanoxic = -0.7 ± 0.2‰。结合先前对海水颗粒和沉积物孔隙流体分析的研究，我们的结果表明 V 主要通过沉降颗粒输送和富集在缺氧沉积物中。海洋沉积物中的自生 V 同位素组成可能受与颗粒结合并溶解在海水中的 V 物种之间的同位素分馏控制，这可能随 V 的形态和吸附特性而变化，而 V 的形态和吸附特性受局部氧化还原条件的强烈控制。此外，Cariaco盆地的euxinic沉积物表现出独特的Δeuxinic = -0.4±0.2‰，这可能受到海水V去除率与海水更新率之间关系的影响。我们的结果强调了自生海洋沉积 V 同位素组成与上覆局部氧化还原条件之间的直接联系。这项对现代海洋环境中 V 同位素的调查为利用 V 同位素重建古代氧化还原波动提供了一个初步框架，