REESources · experimental investigation of the role of fluids in the formation of rare metals ore deposits.

REESources: experimental investigation of the role of fluids in the formation of rare metals ore deposits.

Rare Earth Elements (REE) have become an essential resource for the transition to a carbon-free economy. Meeting the increasing demand for these critical metals requires a fundamental understanding of the geological processes that enable REE concentration in the Earth’s crust. In a very schematic way, the enrichment process leading to the concentration of REE up to economic grade can be divided into 3 phases: (1) a magmatic enrichment phase that involves fractional crystallization of carbonatite, syenite or granite melts, (2) an hydrothermal enrichment phase that involves high-temperature fluids that mobilized and transport the REE out of their magmatic host minerals and reprecipitates them as newly enriched minerals in the magmatic intrusion or the host rocks and (3) a weathering phase where low-temperature meteoritic fluids can further concentrate the REE, especially in ion-adsorption clays. The aim of the REESources project was to provide new insights on the magmatic and hydrothermal enrichment phases, using novel experimental designs that enable us to study the behaviour of REE upon magmatic crystallisation and hydrothermal alteration, directly at the high P-T conditions relevant to the formation of REE ore-deposits. Especially, we identified three main research questions to be answered by the REESources project: 1. What is the effect of different ligands (Cl, F, SO42-, CO32-) on the hydrothermal mobilization of the REE? Is there an ideal composition responsible for the enrichment of more valuable HREE over LREE? 2. How are REE extracted from their magmatic source? Is hydrothermal remobilization solely related to the late evolution of alkaline systems (ie., ore-forming fluids are only produced at the very end of the magmatic intrusion’s life) or can early magmatic fluids mobilize REE at T > 500 °C? 3. How are REE elements and their valuable cousins Nb and Ta concentrated in magmatic phases? What is the role of F, but also P in the formation of ore minerals as zircon, pyrochlore or apatite? To answer these questions, I performed a combination of in-situ spectroscopy measurements and piston-cylinder experiments at the European Synchrotron Radiation Facility (Grenoble, France) and the Institute of Mineralogy at the WWU University (Münster, Germany).

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз