Th- and U-bearing minerals in the SE Mediterranean margin of Spain

Abstract

This paper presents the first specific study of the Th- and U-bearing minerals, which were recently found in the SE Mediterranean margin of Spain (El Hoyazo area, Almería province). These minerals are REE phosphates (mainly monazite) which occur as amoeboidal-to-elongate inclusions, from around 10 µm to 120 µm, hosted in single garnet crystals from dacite lavas and metamorphic rocks from the El Hoyazo Volcanic Complex. Th and U contents are higher than 1 wt%, with 3.04 to 5.62 wt % for ThO2, and 0.7 to 1.75 wt% for UO2. Both elements are also found in xenotime (ThO2: 0.24, UO2: 0.27 wt%). Given that the erosion of the volcanic source rocks has generated a "placer-type" deposit of monazite sands and that garnets (main carriers of monazite) are being commercialised, an environmental monitoring and management plan should be urgently executed in the area.