Art of the Possible: High Energy Synchrotron X-Ray Radiation for Mine Tailings Characterization in Re-mining Operations

G. Ray
Cornell High Energy Synchrotron Source, Cornell University,
United States

Keywords: resource extraction, synchrotron, X-ray, hyperspectral imaging, diffraction, spectroscopy and imaging, rare earths, critical minerals, REE, CM, mine tailings, re-mining, domestic supply chain


Rare earth elements and critical minerals (REE/CM) sit atop the list of resources our nation critically requires, but currently cannot domestically produce at volumes necessary to sustain innovation. Ore tailings sites across the U.S. may provide access to millions of metric tons of REE/CM, however, current industry techniques for characterizing and understanding composition and concentration fall short in providing targeted quantitative and spatial intelligence for discovery, extraction and remediation operations. Traditional techniques such as multi-element geochemistry, microscopy, and SEM-based quantitative methods (QEMSCAN, TIMA, MLA) provide some insight, but they suffer from resolution, chemical analysis and modeling limitations that impede their capability to adequately characterize tailings sites. X-Ray tools developed for fundamental materials science at the Cornell High Energy Synchrotron Source (CHESS) may address these issues to improve re-mining operations, decision making and economic risk management. CHESS, one of five facilities of its type in the world, is a high-energy synchrotron producing hard x-rays that can interrogate tailings samples using diffraction, spectroscopy and imaging methodologies not possible at typical laboratory scales. At present, CHESS can effectively quantify rare earth elements (µg/cm2) at “bulk”, or >100µm, spatial resolution utilizing x-ray fluorescence (XRF) at 65+ keV with existing single channel Ge detectors. XRF mapping at 10-20 keV with a Vortex ME4 detector and compound refractive lenses or capillary focusing can characterize accessory elements to 10-100 µm. For thin samples, x-ray transmission modes can accomplish x-ray diffraction bulk or microbeam mapping for complementary mineral phase identification. Further, a coarse resolution hyper spectral reflectance setup supporting XRF mapping is currently being prototyped. This coupled with hyperspectral imaging and XRF mapping tools can interrogate samples ranging from laboratory scale all the way to large-area industrial sites. Looking out three-to-five-years, two cutting edge tools will enable even greater innovation at CHESS. First, the dedicated High Magnetic Field (HMF) beamline, featuring a 20 Tesla low-temperature superconducting magnet — one of the strongest magnets on the planet — will enable precision studies of materials in persistent magnetic fields that vastly exceed those available at any other synchrotron. Second, a world-class micro focusing beamline specialized for XRF imaging and x-ray absorption spectroscopy, with submicron spatial resolution, high flux and multimodal imaging options will be available. This will provide a quantitative method for 2D- and 3D spatially resolved elemental and ionomic measurements with access to chemical bonding environments of specific elements. These measurements typically require minimal sample preparation, enabling direct, quantitative, high-throughput, spatial concentration measurements. This presentation provides an overview of CHESS’ disruptive tools and methodologies that imagine a paradigm shift in future re-mining operations across our nation’s landscape. CHESS’ capabilities will provide improved understanding of the microscale deportment of REE/CM’s chemical environment, size and quantities, enabling predictions essential for industrial partners to develop extraction processing workflows. These capabilities will accelerate technology transfer of fundamental science to industry-scale assets that unlock a future characterized by U.S. REE/CE global competitiveness and national supply chain security.