Rare Earth Elements and Yttrium in Geothermal Fluids

Abstract

The series of rare earth elements and yttrium (REY) is a useful tool in tracing the origin of fluids, which is fundamental in understanding any fluid-rock system. The suite of REY enables to study the source of fluids, the state of equilibrium in water-rock interaction, and changes of fluid composition by both precipitation of scale during ascent and by dissolution of scale particles during sampling of liquids and vapours. Knowing the amount of scale formation and the distribution of REY between liquid and scale, the REY abundance in the original fluid under bottom hole conditions can be back-calculated. Partition factors of elements between vapour and liquid increase from alkalis to earth alkaline elements to REY. Significant fractions of REY are transported by CO2 rich vapour.