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Key Points:</br>
<b>Geochemical Dichotomy of Lunar Soils</b>: 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.
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<b>Cadmium (Cd)</b>: 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.
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<b>Thermal Neutron Capture</b>: Thermal neutron capture by 113Cd, induced by galactic cosmic rays impacting the lunar surface, helps reconstruct the duration of exposure to space weathering.
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<b>Cadmium stable isotope fractionation</b>: 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.
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<b>Implications for Lunar History and Material Origin</b>: 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.