Replication Data for: Cadmium isotope fractionation and neutron capture effects in lunar samples

Key Points: Geochemical Dichotomy of Lunar Soils: Early studies of Apollo lunar soils show a geochemical dichotomy, dominated by mare and highland lithologies with varying admixtures of material from the Procellarum KREEP Terrane. Cadmium (Cd): This study uses the volatile element cadmium to identify sources and origins responsible for mass dependent stable isotope fractionation and assess the effect of space weathering at the lunar surface. Cadmium concentrations and isotopic compositions are reported for samples from the Apollo 12, 16, and 17 missions. Thermal Neutron Capture: Thermal neutron capture by 113Cd, induced by galactic cosmic rays impacting the lunar surface, helps reconstruct the duration of exposure to space weathering. Cadmium stable isotope fractionation: Percent scale variations in Cd stable isotopes are observed, with e112/110Cd ranging from ~0 to +106 in mare soils, from +60 to +97 in highland soils. Orange glass 74220 exhibits an isotopically light enrichment (e112/110Cd = -27). The anorthosites have contrasting e112/110Cd (-107 vs. +47). Thermal neutron capture effects are larger in the old highland than the mare soils, possibly reflecting a compositional effect but mostly a longer exposure history to GCR. Implications for Lunar History and Material Origin: The findings of Cd isotopic compositions in immature KREEP-rich soils similar to that of the Bulk Silicate Earth suggest an origin for the KREEP material either as excavated material from the Copernicus crater or a vapor redistributed at the lunar surface. This comprehensive Cd isotope dataset provides a framework for future Cd isotope studies aiming to further our understanding on the distribution and origin of volatile elements in the Earth-Moon system.

核心要点：月球土壤的地球化学二分性
早期针对阿波罗（Apollo）月球土壤的研究表明，其存在地球化学二分性，主要由月海与高地岩性构成，并混杂有不同比例的风暴洋克里普地体（Procellarum KREEP Terrane）物质。
镉（Cd）：本研究选取挥发性元素镉（Cd），用以甄别引发质量依赖性稳定同位素分馏的物源与成因，并评估月球表面空间风化的作用效应。本研究报道了阿波罗12号、16号及17号任务所获样品的镉浓度与同位素组成。
热中子俘获（Thermal Neutron Capture）：银河宇宙射线轰击月球表面可诱导¹¹³Cd发生热中子俘获反应，该过程有助于重建月球表面遭受空间风化暴露的持续时长。
镉稳定同位素分馏（Cadmium stable isotope fractionation）：观测到镉稳定同位素存在百分比级别的变异：月海土壤的ε¹¹²/¹¹⁰Cd值介于~0至+106之间，高地土壤则介于+60至+97之间；橙色玻璃样品74220表现出同位素轻富集特征（ε¹¹²/¹¹⁰Cd = -27）；斜长岩样品的ε¹¹²/¹¹⁰Cd值则呈现显著差异，分别为-107与+47。
热中子俘获效应在古老高地土壤中强于月海土壤，这可能反映了物质组成差异，但更主要的原因是其遭受银河宇宙射线（Galactic Cosmic Rays, GCR）暴露的历史更久。
月球演化与物质成因的启示：未成熟富克里普土壤的镉同位素组成与整体硅酸盐地球（Bulk Silicate Earth）相似，这表明克里普物质的成因要么源自哥白尼撞击坑（Copernicus Crater）的挖掘物质，要么是月球表面经气相再分配形成的产物。这套完整的镉同位素数据集为未来的镉同位素研究提供了研究框架，以期进一步增进我们对地月系统中挥发性元素分布与成因的认知。