Solubility of orthophosphates in crustal fluids: mechanisms of rare earth elements and actinides mobilization in high- and low-temperature environments

• Grant number: 25/06483-0
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: September 01, 2025
• End date: April 30, 2029
• Field of knowledge: Physical Sciences and Mathematics - Geosciences
• Principal Investigator: David Jozef Cornelius Debruyne
• Grantee: Deusavan Sales da Costa Filho
• Host Institution: Instituto de Geociências (IG). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

This doctoral research proposal aims to investigate, at nano- and microstructural scales, the mechanisms of coupled dissolution-precipitation and isomorphic substitution in orthophosphates of rare earth elements (REE) and actinides (U, Th), under low- to medium-temperature hydrothermal conditions. The focus is to understand how minerals such as monazite-(Ce), xenotime-(Y), thorite, and zircon respond to fluid-rock interaction processes in crustal environments, particularly in Brazilian pegmatitic and granitic systems. The project is relevant to both fundamental mineralogy and applied fields such as geochronology, strategic element metallogenesis, and the environmental behavior of radionuclides.The study will combine advanced analytical techniques, including scanning and transmission electron microscopy (SEM, TEM, EBSD), Raman spectroscopy, cathodoluminescence, U-Pb dating via LA-ICP-MS, and thermodynamic modeling using GEM-Selektor. The main samples will be sourced from three key Brazilian sites: Serra Dourada Granite (Goiás), the Rondônia tin province, and the Madeira deposit (Amazonas). The goal is to build alteration models that account for fluid composition, especially fluoride-rich fluids, textural evolution, and elemental redistribution, with a focus on the differential mobility of U, Th, and REE under realistic geological conditions.The research is supervised by Prof. Dr. David Debruyne (UNICAMP), with co-supervision and international collaboration from Prof. Dr. Nilson Botelho (UnB) and Dr. Daniel Harlov (GFZ Potsdam). The work plan is organized over four years and includes field sampling, laboratory analyses, integrated data interpretation, and scientific writing. At least three publications in high-impact international journals are expected as outcomes.The results will provide new insights into mineral stability and critical element mobility under natural geological conditions, with direct applications to REE exploration, nuclear waste repository assessment, and geochemical modeling of acidic tropical environments. In addition, the proposal has a strong training component, contributing to the scientific and technological advancement of strategic topics for Brazil's mineral sovereignty and the energy transition. (AU)