HANDHELD X-RAY FLUORESCENCE INSTRUMENT IN EXPLORATION AND DEVELOPMENT OF RARE EARTH ELEMENTS

Handheld X-ray fluorescence (pXRF) provides rapid, non-destructive chemical analyses in the field. This study evaluates the merits/limitations of pXRF technology in exploration for REE-bearing deposits. It is based on the Thermo Scientific Niton XL3t GOLDD+ analyzer, the Standard Reference Material NIST 2780 from the National Institute of Standards and Technology (Gaithersburg, USA), the Certified Reference Material “TRLK” Rare Earth Ore “CGL 124” from the Mongolia Central Geological Laboratory, the Reference Niobium Ore OKA-1 (CANMET), and a 99.8% silica blank from Alpha Aesar (Ward Hill, USA). Each standard was analysed more than 100 times. These analyses, in combination with two orientation surveys, an inventory chemical signatures of the main REE deposit-types, and compilation of ore grade data from 37 most advanced REE project outside of China, indicates that the pXRF is suitable for use in exploration and development of carbonatite-related REY deposits such as Mountain Pass (California, USA), Bayan Obo (Inner Mongolia), Wicheeda Lake, St. Honoré, and Eldor (Canada) and peralkaline intrusion-related deposits, such as Kipawa, Nechalacho and Strange Lake (Canada). By extension, the pXRF is also suitable for the exploration of apatite-monazite veins such as Steenkampskraal (South Africa). A commercial pXRF, without a radioactive source, cannot analyze effectively for most of the heavy lanthanides; however, Y can be used as a pathfinder for these elements. Limited, but effective use of pXRF in exploration for ion adsorption clay deposits such as those of Xinxui and Heling areas (China) that can grade as low as 500 ppm total REY also appears possible. The pXRF can definitely be used for delineation of REE-enriched zones within the sedimentary phosphate deposits and probably for estimation of REY concentrations in “Quartz-pebble conglomerate” (Elliot Lake, Canada) type uranium deposits. Deposit-type specific orientation studies, prior to initiation of a large field programs are recommended.