Dr. Alexander Gysi

Ore Deposits and Critical Minerals Research Group

Hannah Juan Han
Research Scientist II

Stability of aqueous REE hydroxyl complexes at hydrothermal conditions

I am interested in the stability of aqueous REE hydroxyl complexes at hydrothermal conditions. My research mainly focuses on the hydrothermal laboratory experiments and a combination of these hydrothermal experiments and thermodynamic modeling to develop an internally consistent thermodynamic database for aqueous REE species using the program GEMS. The hydrothermal experiments will conducted to determine the hydrolysis constants of the aqueous REE hydroxyl complexes under high temperature conditions. These results will provide accurate fundamental thermodynamic information for improving the thermodynamic database and thus develop a new predictive model for aqueous REE hydroxyl complexes in natural system. I am also interested in understanding the behaviors of REE species at hydrothermal conditions using different kind of analytical instruments including ICP-OES, ICP-MS, IC and so on.

Bryan Maciag
Postdoctoral Fellow in Experimental Geochemistry

High temperature and pressure speciation of REE in supercritical fluids

My primary research interest is in understanding the fundamental chemical behavior of rare earth elements (REE) in geological systems. The first aspect of my research is investigating the chemical form (speciation) of Nd and Yb in supercritical aqueous fluids. For this research, I will use hydrothermal diamond anvil cell experiments to simulate geological conditions and measure the speciation in-situ using both Raman spectroscopy and synchrotron-based X-ray absorption spectroscopy. The second aspect of my research will investigate the solubility of Yb-phosphates in supercritical aqueous solutions using batch-type dissolution experiments. Fundamental thermodynamic data will be derived from these experiments and incorporated into the MINES database. Together these two research aspects will further develop our understanding of REE behavior in geological systems, and illuminate the processes of REE ore deposit formation.

Evan Owen
MS student in Geochemistry

Geochemistry and mineral paragenesis of REE and fluorite bearing veins and breccias in the Gallinas Mountains

My interests include the genesis of hydrothermal ore deposits and related alteration styles, as well as geochemical methods in mineral exploration, with a focus on critical minerals. My M.Sc. thesis research will involve studying the geochemistry and mineral paragenesis of REE and fluorite bearing veins and breccias in the Gallinas Mountains here in New Mexico. I also plan to characterize the various modes of alteration found there, develop a practical deposit model, and show that alteration can be used to vector towards REE mineralization. When I’m not busy with coursework and research, I enjoy mineral collecting, hiking and backpacking, and music.

Kevin Padilla
PhD student in Geochemistry

Solubility and aqueous speciation of REE in hydrothermal fluids

My research interest includes experimental studies of the solubility and aqueous speciation of REE at hydrothermal conditions and, particularly, the evaluation of the thermodynamic stability of chloride- and hydroxyl-bearing aqueous species of light/heavy REE at different pH and temperature conditions. The results of my research project will be used to improve the thermodynamic database for REE species and to model the mobility and precipitation of critical minerals. I am enjoying this science teamwork as much as being in my favorite natural environment.

Yerko Figueroa Penarrieta
PhD student in geochemistry

Speciation of REE hydroxyl complexes in hydrothermal aqueous fluids: Experimental data and thermodynamic calculations

My interest includes the geochemistry and behavior of REE in hydrothermal fluids and the ore-forming processes. The thesis research consists of experiments and modeling of the aqueous speciation of REE hydroxyl complexes with different pH and temperature conditions. The main goal is to generate a consistent thermodynamic dataset for those aqueous species based on experimental data with a focus on ore-forming processes. Besides research, I enjoy traveling to natural parks, hiking, and music.

Sarah Smith-Schmitz
Postdoctoral Fellow in Experimental Geochemistry

Speciation of Rare Earth Elements (REE) in supercritical aqueous fluids

My primary area of research is experimental analysis of REE coordination chemistry in supercritical aqueous fluids. My goal is to identify and characterize REE complexes in aqueous solution with a variety of ligands as functions of ionic strength and pH under supercritical conditions. The first branch of my research consists of hydrothermal diamond anvil cell experiments using in situ synchrotron based XAS to characterize ion solvation and coordination of aqueous complexes for REE in supercritical aqueous fluids. The data from this work, in conjunction with AIMD simulations, will establish the coordination chemistry of REE. The second branch of my research consists of supercritical aqueous solubility and speciation experiments using high temperature- pressure flow-through UV-Vis and capillary Raman spectroscopy techniques. These experiments will generate fundamental thermodynamic data that will be incorporated into the MINES database and can be used to develop more accurate predictive models for the behavior of REE in the natural world e.g., magmatic-hydrothermal systems.

Aadish Velmani
MS student in Geochemistry

(project pending)

My area of research includes experimental and field study of rare earth elements enriched fluorite and its genesis through hydrothermal processes. The goal of this study is to determine different generations of REE-bearing fluorite from the Gallinas Mountains REE-fluorite deposit in New Mexico, and study the type and compositions of fluid inclusions hosted in them. The second part of my study is to synthesize hydrothermally REE-doped fluorite to study the partitioning behavior and mobility of REE between fluorite and aqueous fluids. Aside from my research, I am an avid reader, mineral collector, and musician.

Previous Students and Post-Docs

• Ruiguang Pan, Postdoctoral Fellow in Computational Thermodynamics
  (now at Indiana University, Bloomington)
• Deusavan Costa Filho, MS in Geochemistry
  Report: "Hydrothermal REE partitioning between calcite and aqueous fluids at 150°C"
• Madison Payne, MS in Geochemistry
  Thesis: "Hydrothermal REE partitioning experiments between fluorite and aqueous fluids at 100 to 250°C"