STANDARDIZING A FIELD SCREENING PROTOCOL USING PORTABLE X-RAY FLUORESCENCE AND RADIATION SPECTROMETRY TO ASSESS CRITICAL MINERAL COMMODITIES IN HEAVY MINERAL PLACERS: HOW CAN WE BETTER STREAMLINE DECISIONS IN THE FIELD?

The Virginia Department of Energy (Virginia Energy) Geology and Mineral Resources Program is working collaboratively with the U.S. Geological Survey Earth Mapping Resources Initiative (Earth MRI) program and the U.S. Bureau of Ocean Energy Management to assess heavy mineral sands contained in paleo-placer deposits on Virginia’s Coastal Plain and offshore in shallow marine sediments. These heavy minerals are known to contain critical mineral commodities such as titanium (Ti), zirconium (Zr), and rare earth elements (REE). Technologies such as portable X-ray fluorescence (pXRF) and portable gamma spectrometry may provide a cost-effective means of acquiring semi-quantitative results in the field that can be compared with geochemical and mineralogical data from laboratory analyses. Portable gamma spectrometer results can also be used to assist in ground-truthing regional aerial radiometric survey data that indicate the presence of thorium-bearing minerals, such as monazite.

A rapid field screening protocol is being developed using a SciAps X-555 pXRF analyzer and Radiation Solutions RS-125 portable gamma spectrometer to assess the presence of heavy minerals such as monazite, ilmenite, rutile, and zircon. Initial data from our pXRF scans of heavy mineral concentrates (HMC) and the bulk sediment samples containing heavy minerals indicate positive correlations between elevated Ti, Zr, Ce and La. These results show similar correlations with laboratory analytical results for major and trace elements. The pXRF data are also useful to compare with mineral compositions provided by automated mineralogy laboratory techniques such as TESCAN Integrated Mineral Analyzer (TIMA). We are evaluating key factors that impact the pXRF results such as the concentration and interference of target elements (e.g., low REE, iron masking), sample heterogeneity, moisture content, calibration criteria, and optimal scan time settings. By identifying where the setbacks and areas for further validation are needed, the protocol can deliver greater utility for use in the field and in industry.