Collaborative Research: Iron and Molybdenum Isotope Fractionation During Mineral Weathering

该提案寻求资金，用于研究在最基本的生物地球化学过程之一：矿物风化过程中铁和钼同位素的分馏。我们打算在一系列模拟自然界风化过程的受控实验室实验中，研究有机配体和细菌对从氧化物和硅酸盐中浸出的铁和钼同位素组成的影响。最近的分析进展首次揭示了这两种元素的同位素组成的显著自然变化。特别是在铁的情况下，补充的实验室研究已经提供了关于分离机制的信息，包括微生物介导的铁还原过程中的分离（111）。这些研究表明，铁同位素系统可以为研究古沉积物的生物活性和研究铁的生物地球化学循环提供有力的工具。Mo同位素系统提供了类似的可能性。由于这两种金属的独特生物重要性，以及它们对环境条件的极端敏感性，从铁和钼同位素研究中获得的见解可能在地球科学中具有广泛的用途。尽管风化在这两种金属的环境地球化学中具有明显的重要性，但在风化过程中这两种金属的分异尚未得到研究。初步数据表明，当涉及生物调解时，这可能是铁同位素分馏的一个特别重要的过程。此外，虽然已经确定了一些能够分离金属同位素的过程，但对这种分离的化学机制仍然知之甚少。这项研究将由宾夕法尼亚州立大学的Susan Brantley小组和罗切斯特大学的Ariel Anbar小组合作进行。布兰特利在研究有机配体和细菌对矿物风化的影响方面有着良好的记录；安巴尔在这项研究所需的高精度同位素测量方面有着良好的记录。

This proposal seeks funding for research into the fractionation of iron and molybdenum isotopes during one of the most fundamental biogeochemical processes: Mineral weathering. We intend to investigate the effects of organic ligands and bacterial on the isotopic composition of Fe and Mo leached from oxides and silicates in a series of controlled laboratory experiments that mimic weathering processes in nature. Recent analytical advances have revealed, for the first time, significant natural variations in the isotopic compositions of both these elements. In the case of Fe in particular, complementary laboratory studies have provided information on fractionation mechanisms, including fractionation during microbially-mediated reduction of FE (111). These studies suggest that the FE isotope system could provide a powerful tool for studying biological activity in ancient sediments, and/or research into the Fe biogeochemical cycle. The Mo isotope system offers similar possibilities. Because of the unique biological importance of both these metals, and their extreme sensitivity to environmental conditions, the insights gained from Fe and Mo isotope studies are likely to be of broad utility in the geosciences. The fractionation of neither metal has been studied during weathering, despite the obvious importance of weathering in the environmental geochemistry of these metals. Preliminary data indicate that this could be a particularly important process for Fe isotope fractionation when biological mediation is involved. In addition, while some processes capable of fractionating metal isotopes have been identified, the chemical mechanisms of such fractionation remain poorly understood. This research will be conducted collaboratively between Susan Brantley's group at Pennsylvania State University, and Ariel Anbar's group at the University of Rochester. Brantley has a demonstrated track record studying the effects of organic ligands and bacteria on mineral weathering; Anbar has a demonstrated track record with high-precision isotopic measurements of the type required for this research.