Refining the sedimentary pyrite proxy: Applications for understanding past ocean chemistry

精炼沉积黄铁矿代理：了解过去海洋化学的应用

• 批准号: RGPIN-2019-04843
• 负责人: Gregory, Daniel
• 金额: $ 1.82万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=714807
• 关键词: Refining; sedimentary; pyrite; proxy; Applications

This proposal funds the development of the pyrite proxy tool for ocean chemistry studies. Our oceans hold the key to the beginning and evolution of life on Earth. Paleo-ocean studies can provide not only clues on how life evolved on Earth, but also how to identify exoplanets that may also support life. The research outcomes will also feed into economic geology, with applications in mineral exploration and mining practices. The use of LA-ICPMS analysis of pyrite for ocean chemistry offers several benefits over traditional bulk sample proxies: 1) the in-situ analysis allow only one mineral to be examined, thus excluding the mixed geochemical signatures from coexisting minerals; 2) the technique allows sample selection by mineral texture, which means only the early stage pyrite grains are considered; and 3) since pyrite TE content may be preserved up greenschist facies, more basins can be included in our investigations, especially during the Precambrian. While this pyrite proxy tool is an enticing breakthrough, there are still several aspects that must be assessed before it can be widely implemented in both paleo-ocean. First, the degree to which TEs vary within a sedimentary basin and under different local redox conditions is an important aspect that is poorly understood. We will systematically investigate the TE content of pyrite along transects across well studied sedimentary basins to see how TE content of pyrite varies from near shore to deep water settings. We will also conduct Fe speciation, S-isotope, and whole rock trace and major element analyses on the same samples as the pyrite analyses to unravel how depositional redox conditions affect the pyrite TE content. The ability of pyrite to preserve its TE content through metamorphism means the pyrite TE proxy has the potential to allow additional (metamorphosed) sedimentary basins to be considered for ocean chemistry studies, especially important in the Precambrian. However, it has not been thoroughly tested whether the TE content of pyrite in the unaltered, innermost core of a metamorphosed sample is indeed the same as unmetamorphosed sedimentary pyrite. Using pyrite from sedimentary basins that have experienced contact metamorphism, we will compare the TE content of sedimentary pyrite and cores of metamorphosed pyrite to determine whether the TEs are preserved through metamorphism. The project will then be expanded to examine regional metamorphism. We will use a series of nano- and micro-analytical techniques (LA-ICPMS, TEM, APT, nanoSIMS, and XANES) to detail how TEs are hosted in pyrite. The use of APT to characterise how TEs are held in pyrite in 3D space at the atomic scale will provide invaluable data for other pyrite-related studies, such as metallurgy and mine site reclamation. The data generated through this study with further support mineral exploration studies in developing geochemical targeting tools by establishing a TE range for background, unmineralized pyrite.

该提议资助了用于海洋化学研究的黄铁矿代理工具的发展。我们的海洋是地球生命开始和发展的钥匙。古海洋研究不仅可以提供有关地球生命如何发展的线索，还可以提供如何识别可能支持生命的系外行星。研究成果还将以矿产勘探和采矿实践的应用为经济地质。在海洋化学中，使用LA-ICPMS分析提供了比传统批量样本代理的几个好处：1）原位分析仅允许检查一种矿物，因此将混合的地球化学特征排除在共存矿物之外； 2）该技术允许通过矿物质纹理进行样品选择，这意味着仅考虑早期黄铁矿晶粒； 3）由于可以保存黄铁矿的含量，因此可以将更多的盆地包含在我们的研究中，尤其是在前寒武纪期间。 尽管该黄铁矿代理工具是一个诱人的突破，但仍有几个方面必须在两种古ocean中广泛实施之前进行评估。首先，在沉积盆地和在不同的局部氧化还原条件下变化的程度是一个重要的方面，知之甚少。我们将系统地研究横跨经过良好研究的沉积盆地的横除横断面的黄铁矿的Te含量，以了解黄铁矿的TE含量如何从近海岸到深水环境变化。我们还将对与黄铁矿分析相同的样品进行FE形成，S-同位素和整个岩石痕迹以及主要元素分析，以揭示沉积氧化还原条件如何影响黄铁矿TE含量。 黄铁矿通过变质而保存其TE含量的能力意味着黄铁矿TE代理具有允许考虑海洋化学研究的额外（变质）沉积盆地的潜力，在前寒武纪尤其重要。然而，尚未彻底测试黄铁矿在未改变的，最内向的核心样品中的含量是否与未塑形的沉积黄铁矿相同。使用经历过接触变质的沉积盆地的黄铁矿，我们将比较沉积黄铁矿和变形黄铁矿的TE含量，以确定是否通过变质保存TES。然后将扩大该项目以检查区域变质。 我们将使用一系列纳米和微分析技术（LA-ICPMS，TEM，APT，Nanosims和Xanes）来详细说明如何在黄铁矿中托管TES。在原子量表以3D空间中的3D空间中的黄铁矿中持有TE的使用将为其他与黄铁矿相关的研究（例如冶金和矿场站点填海）提供宝贵的数据。通过这项研究生成的数据通过进一步支持矿物勘探研究，以通过建立用于背景的无矿化黄铁矿的TE范围来开发地球化学靶向工具。