The geochemical behaviour of Sn and In during mantle melting and crust formation

铟和锡属于中等到高度挥发性和中等亲铁/亲硫元素组的一部分。在行星吸积过程中，这些元素被认为在核心形成时部分地被清除到核心中，并通过晚期的薄板被额外地输送到早期地球。例如，由于类似的挥发性亲石元素的丰度，铟是极少数在地幔中比预期更丰富的元素之一，而锡似乎略有贫化。然而，缺乏关于这些元素在主要陆相硅酸盐储集层中分布的高质量数据，以及缺乏关于锡和铟在地质过程(例如地幔熔融和地壳形成)中的行为的系统研究，目前阻碍了对地幔丰度的足够准确的估计。传统上，这样的估算是基于长期以来被认为在火成岩过程中不分离的锡/Sm和In/Y元素对。然而，最近关于火成岩的锡-铟数据似乎表明，在一些重要的情况下，尤其是在俯冲带，这些元素比率是高度分馏的。该项目的目的是获得关于经过精心表征和精心挑选的橄榄岩和原始玄武岩的高精度In-Sn数据，以便对以下情况有重要的了解：(1)In和Sn在地球硅酸盐储集层和原始地幔中的分布；(2)它们在地球主要分异事件期间的行为，并评估In和Sn作为这类事件(如晚期岩块)示踪剂的潜力；以及(3)控制In和In的富/贫化过程及其从类似不相容的微量元素如Sm和Y中的分馏。

Indium and tin are part of the moderately to highly volatile and moderately siderophile/chalcophile element group. During planetary accretion, these elements are thought to have been partially scavenged into the core as it formed and additionally delivered to the Early Earth by the Late Veneer. Indium, for example, is one of the very few elements that are more abundant in the terrestrial mantle than expected from the abundance of similarly volatile lithophile elements whereas Sn appears to be slightly depleted. However, the scarcity of high-quality data on the distribution of these elements in major terrestrial silicate reservoirs as well as the lack of systematic studies on how Sn and In behave during geological processes (e.g. mantle melting and crust formation), currently hamper sufficiently accurate estimates on the mantle abundances. Traditionally, such estimates were based on the Sn/Sm and In/Y element pairs that were long considered to be unfractionated during igneous processes. More recent Sn-In data for igneous rocks, however, appear to indicate that these element ratios are highly fractionated in some important cases, and especially in subduction zones. This project aims to obtain high-precision In-Sn data on well-characterized and carefully selected peridotites and primitive basalts in order to give important insights into (1) the distribution of In and Sn in the Earth's silicate reservoirs and the primitive mantle, (2) their behaviour during the major differentiation events of the Earth and assess the potential of In and Sn as tracers for such events, e.g., the Late Veneer, and (3) the processes that control the enrichment/depletion of Sn and In and their fractionation from similarly incompatible trace elements like Sm and Y.