Determination of mercury isotope compositions in chondritic meteorites

汞（Hg）比其他高挥发性金属（如Cd、Tl或Pb）更易挥发，但比水等冰的挥发性小。到目前为止，只有两个汞同位素数据的相当原始的默奇森和阿连德石（劳雷塔等人，2001年），很少有准确的汞丰度数据公布的汞。在当时可能的中等精度范围内，相对于陆地标准，没有观察到两种汞矿的汞稳定同位素分馏。最近的汞同位素研究，重点是天然陆地和实验样品，表明许多过程，包括挥发和平衡分配之间的蒸汽和液体汞与质量相关的同位素分馏（MIF）和质量无关的（MIF）。此外，镉和锌稳定同位素分馏经常观察到的陨石。汞的挥发性非常高，在陆地和实验样品中存在汞的微量元素和微量元素干扰因子，以及其他挥发性金属存在微量元素干扰因子，这些都表明汞同位素为影响早期太阳系中挥发性元素和冰的过程提供了一种有前途的示踪剂。因此，汞同位素宇宙化学可能有助于了解初级挥发性元素的耗尽，挥发性元素的二次再分配，例如在母体上，以及类地行星中挥发物的来源。此外，我们将应用酸浸和部分热汞释放至少默奇森CM 2球粒陨石，以推断是否可测量的核合成汞异常生存处理在早期的太阳系。一个全面的需求，高精度和准确的研究汞同位素在球粒陨石需要非常复杂的分析方法的设置。初步工作的汞分离岩石粉末使用直接汞分析仪和汞同位素分析的冷蒸气MC-ICP-MS的第一个结果报告在此建议。

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.