Calibration of the phosphate δ18O thermometer for SIMS analyses to reconstruct ancient seawater temperatures

校准用于 SIMS 分析的磷酸盐 δ18O 温度计以重建古代海水温度

• 批准号: 470134482
• 负责人: Professor Dr. Thomas Wotte
• 金额: --
• 依托单位: Lehrstuhl für Paläontologie / Stratigraphie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/470134482?language=en
• 关键词: Calibration; phosphate; 18O; thermometer; SIMS

Oxygen isotope (δ18O) studies on marine biological precipitated phosphate (bioapatite) provide a valuable tool for reconstructing temperatures of (paleo)seawater. Whereas the conventional oxygen isotope analysis of bioapatite via IRMS (isotope ratio mass spectrometry) requires large sample volumes of > 1 mg, this volume is essentially reduced during in situ SIMS (secondary ion mass spectrometry) analysis. Such a reduction of sample size also minimizes the risk of contamination of the primary oxygen isotope signal. Despite this obvious advantage, some critical points probably influencing the final interpretation of data: (1) There seems to be an offset between oxygen isotope values generated via SIMS and IRMS, as SIMS probably not only liberates oxygen isotopes related to the PO43− group. Whether (and if so, to what extent) non-PO43− related oxygen isotopes bias the final δ18O values or whether this reported offset is only an artefact of sample alteration, needs clarification. (2) Equations necessary for reconstructing the (paleo)seawater temperatures are based on data from IRMS analyses. But, are these thermometer equations also applicable for SIMS data? (3) In order to calibrate the oxygen isotope values from bioapatite generated by SIMS, Durango apatite is commonly used as the primary isotope standard. Even if its homogeneity in δ18O is generally accepted, there are still doubts questioning this presumption. This project aims to clarify these critical aspects to calibrate and establish a phosphate δ18O thermometer for SIMS analyses from bioapatite, allowing a precise calculation of seawater temperatures. For the successful realization of the project, we want to analyze teeth of sharks grown up during standardized seawater conditions. Requirements necessary, are given by commercial aquariums. Why we want to use sharks? Sharks are the ideal provider for marine bioapatite, as (1) their teeth are principally composed of flour-apatite, which is most resistant against secondary alteration, and (2) shark teeth are changed continuously and are thus important fossils from marine and terrestrial environments. To determine oxygen isotope fractionation between bioapatite of teeth and seawater, different shark species of the same aquarium will be investigated. On the other hand, the influence of variations in seawater temperature, pH-value, and oxygen isotopic composition on distinct shark species will be detected by using eight basins of four commercial aquariums.Results of our research will be a fundamental base for calculating seawater temperatures of the geological past, using oxygen isotopes of fossil bioapatite generated via SIMS analysis. Therefore, our project is an important contribution towards a better understanding of the interaction between atmosphere, hydrosphere, and biosphere throughout the Earth’s history.

氧同位素（Δ18O）研究海洋生物规定的磷酸盐（生物磷灰石）为重建（古）海水的温度提供了有价值的工具。尽管通过IRMS（同位素比质谱法）对生物磷灰石的常规氧同位素分析需要大量的样品体积> 1 mg，但在原位SIMS（二级离子质谱法）分析期间，该体积基本减少。这种降低样本量还可以最大程度地减少原代氧同位素信号污染的风险。尽管有这一明显的优势，但一些关键点可能会影响数据的最终解释：（1）通过SIMS和IRMS生成的氧同位素值之间似乎存在偏移，因为SIMS不仅可以释放与PO43-组相关的氧同位素。是否（如果是这样，在何种程度上）非PO43-相关氧同位素偏置最终Δ18O值，或者该报告的偏移是否只是样品改变的伪像，需要澄清。 （2）重建（古）海水温度所需的方程是基于IRMS分析的数据。但是，这些温度计方程也适用于SIMS数据吗？ （3）为了校准由SIMS产生的生物磷灰石的氧同位素值，Durango apatite通常用作主要同位素标准。即使普遍接受其在Δ18O中的均匀性，仍然存在疑问质疑这种推定。该项目旨在阐明这些关键方面，以校准和建立磷酸盐Δ18O温度计，以从生物磷灰石进行SIMS分析，从而精确地计算海水温度。为了成功实现该项目，我们希望分析在标准化海水条件下长大的鲨鱼的牙齿。商业水族馆给出了必要的要求。为什么我们要使用鲨鱼？鲨鱼是海洋生物磷灰石的理想提供者，因为（1）它们的牙齿主要由弗洛 - 磷灰石组成，这是对次要变化的最具耐药性，（2）鲨鱼牙齿不断地改变，因此是海洋和地面环境中重要的化石。为了确定牙齿和海水生物磷灰石之间的氧同位素分馏，将研究同一水族馆的不同鲨鱼物种。另一方面，将通过使用四个商业水族馆的八个基础知识来检测海水温度，pH值和氧同位素组成对不同鲨鱼物种的变化的影响。我们研究的重构将是计算过去的地质学的基本基础，用于使用oxygen oxygen oxygen oxopopes of ossil biiopatite nime nime nime nime nime nime nime nime nime nime nime nime nime nime nime nime nime nime nime nime biiopatite biioapatite。因此，我们的项目是对整个地球历史上对大气，水圈和生物圈之间相互作用的更好理解的重要贡献。