LANTHANIDES AND YTTRIUM DETERMINATION IN ROCKS AND MINERALS BY X-RAY-FLUORESCENCE - APPLICATION TO THE GEOCHEMISTRY EXPLORATION OF SUCH ELEMENTS

An analytical methodology combining ionic exchange and X-ray fluoresce nce for yttrium and lanthanides determination in rocks and minerals is described. The sample dissolution is carried out with a HF-HClO4 mixt ure in open system with alkaline minifusion with NaOH in the case of r efractory minerals. A cationic-type-resin in acid medium is used in th e batch exchange process. The dry resin is conditioned on a special ce llulose support for the determination by X-ray fluorescence. The deter mined elements are Y, La, Ce, Pr, Nd, Sm, Eu, Gd and Er. The accuracy of the methodology was determined by using a standard reference rock. The proposed diagram adjusts to the prospective study of such elements particularly in the follow-up or detail slate, where simplicity as we ll as precision and accuracy are needed in the analysis. The analytica l methodology developed was applied to the geochemical study of the no rthern part of ''Las Chacras-Piedras Coloradas'' batholith (San Luis P rovince, Argentina) where there exist interesting mineralizations of r are earths. The results obtained agree with the observations and studi es made by other authors.