The use of partial digestion techniques in pedogeochemical exploration
LE3 .A278 2011
Master of Science
Earth & Environmental Sciences
Partial digestion geochemistry has been used for more than 40 years to detect surface anomalies associated with buried mineralization. These anomalies are created by vertical migration of elements into surface soils from mineralization at depth. Within these soils, the labile elements typically reside in loosely bound sites on soil particle surfaces. Partial digestions leach only these labile elements and tend to suppress geochemical background and increase geochemical contrast, features that should make partial digestion data more interpretable and visually compelling than total digestion data. To investigate what happens during a partial digestion, B-horizon samples from 3 study areas in Nova Scotia were leached using deionized water and analyzed by ICP-MS. The digestions were analyzed every ~30 seconds over a 30 minute leach time, and pH was measured at this same frequency, allowing calculation of the pE over time. Results were compared with those obtained using conventional 2-hour deionized water ‘batch digestions’. The results of these experiments have provided significant understanding of how partial digestion conditions change over time. Essentially, these results conclusively demonstrate that soil sample matrices simultaneously buffer both the pH and pE conditions, precisely because these soil sample buffers overwhelm any chemical controls exerted by the weak partial digestion. Interestingly, the results also demonstrate that trace element concentrations obtained after less than 10 minutes of leaching are typically less impacted by these matrix effects, and thus provide more accurate exploration results and better geochemical contrast than conventional leach times.
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