Aerosol extraction and the direct laser ablation ICP-MS analysis of the fine and ultrafine fractions of regolith

The < 10 µm, < 4 µm, < 2.5 mmm and < 1 µm fractions of eight regolith samples have been extracted as aerosols, then analysed for > 60 elements by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Precision and accuracy rivals that of conventional digestion and ICP-MS analysis for most elements, but the aerosol extraction and ablation approach can be completed within 30 minutes, avoids compromising the sample by screening, column settling, fusion and/or digestion, and includes data for elements such as Br, Cl, I and Se that are conventionally analysed by individual procedures. Major element chemistry and scanning electron microscope (SEM) imagery show the aerosol fractions of regolith are dominated by kaolinite, with quartz in eolian regolith. The aerosol fractions of Si- and Ca-rich regolith have higher trace element concentrations than the coarser fraction (0.45 − 2 mm), but chalcophile elements are depleted in the aerosols of Fe-rich regolith relative to the coarser fraction. Improvements in in-field analytical technology coupled with aerosol extraction mean that fine and ultrafine fraction chemistry can be used to guide mineral exploration programs in close to real time.