Geochemical fingerprints of brannerite (UTi 2 O 6 ): an integrated study
AbstractBrannerite (UTi2O6) is among the major uranium-bearing minerals found in ore deposits, however as it has been long considered as a refractory mineral for leaching it is currently disregarded in ore deposits. Brannerite is found in a variety of geological environments with the most common occurrences being hydrothermal and pegmatitic. On the basis of scanning electron microscopy observations coupled with electron probe micro-analyses and laser ablation inductively-coupled plasma mass spectrometer analyses, this study describes the morphological features and the major- and trace-element abundances of brannerite samples from five hydrothermal and five pegmatitic localities across the w…
Direct synthesis of pure brannerite UTi2O6
International audience; A new method based on the precipitation of uranium(IV) and titanium(IV) hydroxide precursors was developed to prepare pure brannerite UTi2O6 samples. In fact, U(IV) dissolved in HCl (6 mol L−1) was mixed to Ti (IV) alkoxyde before a basification step with an excess of NH4OH to obtain a highly reactive nanometric (U,Ti)(OH)4 powder. The obtained powder was then dried under vacuum, pressed into pellets and finally fired at 1300 °C. This method led to the formation of pure brannerite in contrast to previous reported protocols, which showed the formation of impurities such us UO2 and TiO2. The refined unit cell parameters of UTi2O6 led to a = 9.8113(2) Å, b = 3.7681(1) Å…
Solubility of Monazite–Cheralite and Xenotime in Granitic Melts, and Experimental Evidence of Liquid–Liquid Immiscibility in Concentrating REE
Abstract We provide new experimental data on monazite, xenotime and U–Th-bearing cheralite solubility in slightly peralkaline to peraluminous granitic melts using dissolution and reverse (i.e. recrystallization after dissolution) experiments in water-saturated and flux-bearing (P + F + Li) granitic melts, at 800 °C and 200 MPa. Although a positive correlation between rare earth element (REE) solubility and melt peralkalinity is confirmed, monazite solubilities reported here are much lower than the values previously published. We suggest that the presence of elevated phosphorus concentrations in our melts depresses monazite solubility, principally because phosphorus complexes with Al and alk…