Frank, Mark R.
M.S. (Master of Science)
Department of Geographic and Atmospheric Sciences
Iron oxide-copper-gold (IOCG) and iron oxide-apatite (IOA) deposits are major sources of iron contained within magnetite and/or hematite as well as copper contained within copper-iron sulfides and gold as a native metal. Their formations have been attributed to magmatic, hydrothermal, or a mixture of magmatic-hydrothermal processes. Vanadium can readily substitute into magnetite via ion exchange due to similar atomic radii and charges as iron and has thus been hypothesized to be an effective tracer of hydrothermal or magmatic inputs. To evaluate the mobility of vanadium in a magnetite-hematite-fluid system, experiments on the partitioning of vanadium between magnetite, hematite and a saline hydrothermal fluid representative of natural systems were completed at 150, 200 and 250°C, for 17 - 28 days. Magnetite and hematite were equilibrated with synthetic hydrothermal fluids containing 15 - 19 wt. % NaCl and variable concentrations of VCl3 (0, 100, 300 and 500 μg/g vanadium). A total of 80 experiments were run, completed and analyzed to evaluate the partitioning of vanadium between the 3 phases. Average vanadium concentrations within magnetite and hematite run products increased with increasing temperature and vanadium concentration of the starting fluid. Partition coefficients of vanadium between magnetite and starting fluid were between 19 and 30 for all conditions studied. Vanadium partitioned preferentially into hematite relative to the fluid by a factor of between 8 and 25 at all conditions studied. Vanadium preferred magnetite relative to hematite up to approximately 225 °C where the partitioning between those two phases was then close to unity. The mobility of vanadium in the system and its ability to partition into magnetite and hematite make the use of vanadium as a tracer of magmatic activity problematic. Utilizing the data from this study, the vanadium concentration observed in samples from Candelaria, Kiruna and El Romeral deposits suggest that the hydrothermal fluid would be limited to 100 - 300 μg/g of vanadium. As IOA and IOCG deposits have characteristically low vanadium concentrations, it could indicate hydrothermal processes during or shortly after formation that deplete the deposit in magmatically derived vanadium.
Nederbo, Jeremy Raymond, "Vanadium Partitioning Between Magnetite, Hematite, and A Hydrothermal Fluid: Implications for Iocg and IOA Deposits" (2023). Graduate Research Theses & Dissertations. 7170.
Northern Illinois University
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