研究人员使用第一性原理计算，发现核—幔分异对硒和碲同位素没有明显的分异作用，而早期星子的平衡蒸发会使硒和碲同位素在 BSE 重同位素中富集。BSE 的硫、硒和碲同位素特征表明，原行星分化在建立地球大多数挥发性元素方面起着关键作用，而地球后期增生对 BSE 的挥发性总量没有实质性的贡献。
据了解，地球易挥发性元素的起源备受争议。将块状硅酸盐地球(BSE)中的硫属同位素碳比率与其可能的组成部分——球粒陨石中的碳同位素比率进行比较，可以限制地球挥发物的起源。然而，在很大程度上，这些比较由于原行星分化过程中潜在的同位素分馏而变得复杂。
附：英文原文
Title: Chalcogen isotopes reveal limited volatile contribution from late veneer to Earth
Author: Wenzhong Wang, Michael J. Walter, John P. Brodholt, Shichun Huang, Michail I. Petaev
Issue&Volume: 2023-12-08
Abstract: The origin of Earth’s volatile elements is highly debated. Comparing the chalcogen isotope ratios in the bulk silicate Earth (BSE) to those of its possible building blocks, chondritic meteorites, allows constraints on the origin of Earth’s volatiles; however, these comparisons are complicated by potential isotopic fractionation during protoplanetary differentiation, which largely remains poorly understood. Using first-principles calculations, we find that core-mantle differentiation does not notably fractionate selenium and tellurium isotopes, while equilibrium evaporation from early planetesimals would enrich selenium and tellurium in heavy isotopes in the BSE. The sulfur, selenium, and tellurium isotopic signatures of the BSE reveal that protoplanetary differentiation plays a key role in establishing most of Earth’s volatile elements, and a late veneer does not substantially contribute to the BSE’s volatile inventory.
DOI: adh0670
Source: https://www.science.org/doi/10.1126/sciadv.adh0670