Continuous leach inductively coupled plasma mass spectrometry: applications for exploration and environmental geochemistry

摘要

Continuous leach inductively coupled plasma mass spectrometry (CL-ICP-MS) is a new analytical technique developed to address some of the shortcomings of bulk leach techniques while overcoming the uncertainties associated with interpreting selective extraction data. It provides information on the specific geochemical sites and mineral phases from which elements are being released using real-time data generated by continually analysing progressively reactive solutions from water to 30% nitric acid as they are pumped through a sample directly into a high resolution ICP mass spectrometer. Mineral breakdown reactions can be monitored from the major elements released, thereby eliminating uncertainties related to host phase/trace element associations. By comparing major and minor element release patterns, trace elements can be reliably assigned to host phases. Results from single mineral phases, mixtures of mineral phases, and natural ore samples indicate that the release of elements from specific minerals is not obscured in more complex samples and that reprecipitation and back reactions are not a concern with this method. Scanning electron micrograph (SEM) examination of the reaction products has been used to verify which phases react and to support the CL-ICP-MS data interpretation. Results for natural soil samples indicate that 'false' mobile element anomalies can be identified using CL-ICP-MS and underscore the importance of understanding where trace elements reside in samples used for environmental studies or mineral exploration.