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.

对海洋生物沉淀磷酸盐（生物磷灰石）的氧同位素 (δ18O) 研究为重建（古）海水温度提供了宝贵的工具，而通过 IRMS（同位素比质谱法）对生物磷灰石进行传统的氧同位素分析需要 > 1 的大样本量。 mg，在原位 SIMS（二次离子质谱）分析过程中，该体积基本上减少了，样品量的减少也将风险降至最低。尽管有这个明显的优势，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 可能不会。仅释放与 PO43− 基团相关的氧同位素。非 PO43− 相关氧同位素是否（如果是，在多大程度上）使最终 δ18O 值产生偏差，或者该报告的偏移是否只是一个偏差。 (2) 重建（古）海水温度所需的方程基于 IRMS 分析的数据，但是，这些温度计方程是否也适用于 SIMS 数据？根据 SIMS 生成的生物磷灰石的同位素值，杜兰戈磷灰石通常被用作主要同位素标准，即使其 δ18O 的均质性被普遍接受，但仍存在。该项目旨在澄清这些关键方面，以校准和建立用于生物磷灰石 SIMS 分析的磷酸盐 δ18O 温度计，以便精确计算海水温度。为了成功实现该项目，我们希望分析牙齿。商业水族馆给出了在标准化海水条件下生长的鲨鱼的必要要求。为什么我们要使用鲨鱼作为海洋生物磷灰石的理想来源，因为 (1) 它们的牙齿是。主要由面粉磷灰石组成，其对二次蚀变的抵抗力最强，并且（2）鲨鱼牙齿不断变化，因此是海洋和陆地环境中的重要化石。为了确定不同鲨鱼物种牙齿生物磷灰石与海水之间的氧同位素分馏。另一方面，将使用四个商业池的八个池来研究海水温度、pH 值和氧同位素组成的变化对不同鲨鱼物种的影响。我们的研究结果将成为利用 SIMS 分析生成的化石生物磷灰石的氧同位素计算过去地质海水温度的基础。因此，我们的项目对更好地了解大气、水圈之间的相互作用做出了重要贡献。 ，以及贯穿地球历史的生物圈。