ICP-MS Methods
Trace Element Compositions
Our ICP-MS lab is currently focused on developing techniques for the analysis of trace elements in geological materials. For fine-grained basic to intermediate rocks we use approximately 0.2mg of sample that is digested using a cocktail of concentrated HF, HNO3, and HCl in a 15ml FEP teflon screw top beaker on a hot plate at a temperature of 105 C. Samples are digested over a period of several days and evaporated to dryness. This is followed by several more additions of concentrated HNO3 and subsequent evaporation. The final dilution (nominally 45000 X) before analysis is with 1% HNO3. Calibration of the ICP-MS is facilitated by several well characterized USGS reference materials (BCR-2 and BHVO-2) that are processed in an identical manner to the unknown samples. While this technique works extremely well for fine-grained basaltic rocks, coarser and more evolved rocks (e.g., granites) may not have all of their phases sufficiently digested (e.g., Zircon).
Isotopic Compositions
We are currently in the process of developing techniques to measure Pb and Sr isotopic compositions of rocks and minerals to be used for both geochronology and isotopic tracers of geochemical processes.