Determination of mercury isotope compositions in chondritic meteorites

球粒陨石中汞同位素组成的测定

• 批准号: 248694714
• 负责人: Privatdozent Dr. Frank Wombacher
• 金额: --
• 依托单位: Institut für Geologie und Mineralogie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/248694714?language=en
• 关键词: Determination; mercury; isotope; compositions; chondritic

Mercury (Hg) is more volatile than the other highly volatile metals (e.g. Cd, Tl or Pb), but less volatile than ices like water. So far, only two Hg isotope data for the rather primitive Murchison and Allende chondrites (Lauretta et al., 2001) and very few accurate Hg abundance data are published for chondrites. Within the moderate precision possible at the time, no significant Hg stable isotope fractionation was observed for the two chondrites relative to the terrestrial standard. More recent Hg isotope studies, that focused on natural terrestrial and experimental samples, showed that many processes including volatilization and equilibrium partitioning between vapor and liquid Hg are associated with mass-dependent (MDF) and mass-independent (MIF) isotope fractionations. Furthermore, Cd and Zn stable isotope fractionations are frequently observed in chondritic meteorites. The very high volatility of Hg, the presence of MDF and MIF for Hg in terrestrial and experimental samples and the presence of MDF for other volatile metals all suggest that Hg isotopes provide a promising tracer for processes affecting volatile elements and ices in the early solar system. Thus, Hg isotope cosmochemistry may contribute to the understanding of primary volatile element depletion, secondary redistribution of volatile elements, e.g. on parent bodies, and the source of volatiles in the terrestrial planets. Furthermore, we will apply acid leaching and partial thermal Hg release to at least the Murchison CM2 chondrite to infer whether measurable nucleosynthetic Hg anomalies survived processing in the early solar system.The demand for a comprehensive, highly precise and accurate study of Hg isotopes in chondrites requires the setup of very sophisticated analytical methods. Preliminary work for Hg separation from rock powders using a direct mercury analyzer and first results for Hg isotope analysis by cold vapor MC-ICP-MS are reported within this proposal.

汞(Hg)比其他高挥发性金属(如Cd、Tl或Pb)更易挥发，但比水等冰更不容易挥发。到目前为止，只公布了相当原始的Murchison和Allende球粒陨石的两个汞同位素数据(Lauretta等人，2001年)，而关于球粒陨石的准确汞丰度数据很少。在当时可能的中等精度范围内，没有观察到这两个球粒陨石相对于陆地标准的显著汞稳定同位素分馏。最近对自然、陆地和实验样品进行的汞同位素研究表明，许多过程，包括挥发和气液汞之间的平衡分配，都与质量相关(MDF)和质量无关(MIF)同位素分馏有关。此外，在球粒陨石中还经常观察到Cd和Zn稳定同位素分馏。汞的极高挥发性、陆地和实验样品中汞的MDF和MIF的存在以及其他挥发性金属的MDF的存在都表明，汞同位素为影响太阳系早期挥发性元素和冰的过程提供了一种有希望的示踪剂。因此，汞同位素宇宙化学有助于理解初级挥发性元素的耗竭、挥发性元素在母体上的二次再分配以及类地行星中挥发性物质的来源。此外，我们将对至少Murchison CM2球粒陨石进行酸浸和部分热汞释放，以推断可测量的核合成汞异常是否在早期太阳系的处理过程中幸存下来。要全面、高精度和准确地研究球粒陨石中的汞同位素，需要建立非常复杂的分析方法。在这项提案中，报告了使用直接汞分析仪从岩粉中分离汞的初步工作和用冷蒸汽MC-ICPMS进行汞同位素分析的第一批结果。