The chemical composition of basaltic and anorthositic lunar soil samples determined by ICP-MS

Using quadrupole ICP-MS, we determined the chemical composition of five basaltic Apollo 12 and six anorthositic Apollo 16 soil samples, the cataclastic lunar anorthosite 60015 and the reference samples BHVO-2 and AN-G.

The aim was to evaluate the processes affecting soil compositions and to provide data that allows for accurate spike additions for isotope dilution analyses of volatile elements and double-spike Cd isotope analyses, while consuming only a few mg of precious sample powder. Of the 56 elements analyzed, Ta, W and Bi for BHVO-2 and Be, P, As, Zr, Cd, Sn, Sb, W, Tl, Bi and U for AG-N deviate by more than 20% from reference values (mostly GeoReM). Deviations are not due to secondary fluorite precipitation, but may reflect residual memory and blank issues and incorrect reference data. The latter is evident for Cd in AN-G, as ICP-MS and double-spike data agree within 6%, while the compiled value is 170% higher.

Apollo 16 soils are dominated by feldspathic highland terrane compositions and Apollo 12 soils are dominantly mixtures between mare basalt and Procellarum KREEP terrane compositions. Higher incompatible element abundances in 12032 and 12033 reveal a larger KREEP component. Of the most volatile elements, Tl displays the least variation in soil samples, Cd and especially In scatter more. Their abundances do not correlate with soil maturity, suggesting that micrometeorite bombardment has no major effect on volatile element abundances. In Apollo 12 soils, the Cd and In abundances may be controlled by the basaltic microbreccia or the basalt component, respectively.