Collaborative Research: Iron and Molybdenum Isotope Fractionation During Mineral Weathering

该提案旨在为研究最基本的地球化学过程之一：矿物风化过程中铁和钼同位素的分馏提供资金。 我们打算调查的影响，有机配体和细菌的同位素组成的氧化物和硅酸盐浸出的Fe和Mo在一系列受控的实验室实验，模拟自然界中的风化过程。 最近的分析进展首次揭示了这两种元素的同位素组成的重大自然变化。 特别是在Fe的情况下，补充实验室研究提供了有关分馏机制的信息，包括微生物介导的Fe还原过程中的分馏（111）。 这些研究表明，铁同位素体系可以为研究古沉积物中的生物活动和/或铁地球化学循环提供一个强有力的工具。 Mo同位素系统提供了类似的可能性。 由于这两种金属独特的生物重要性，以及它们对环境条件的极端敏感性，从Fe和Mo同位素研究中获得的见解可能在地球科学中具有广泛的实用性。尽管风化作用在这些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，这两种金属的分馏作用都没有得到研究。 初步数据表明，这可能是一个特别重要的过程，铁同位素分馏时，生物调解参与。 此外，虽然已经确定了一些能够分馏金属同位素的过程，但对这种分馏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.