Magmatic-hydrothermal critical ore systems: identifying fluid sources and tracing fluid evolution

Critical metals are essential to the economy and national defense. However, many critical metal systems are not understood as well as traditional deposits (e.g. porphyry systems). Furthermore, their sources and formation processes are debated. This dissertation investigates how magmatic–hydrothermal fluids associated with critical metal deposits evolve and how to identify their sources. The first study examined the Baiyanghe Be–U deposit in China. Previous studies could not determine whether Be and U are coeval. Radiogenic isotopes and Sm–Nd geochronology shows Be mineralization occurred in two pulses, one at 311 ± 12 Ma sourced from the Yangzhuang rhyolite, and another at 261 ± 3 Ma related to mantle-derived fluids and predates primary U (240 ± 7 Ma). Uranophane ages (305–208 Ma) suggest U mobilization by surface waters occurred throughout the deposit’s history. This new timeline resolves a long-standing question about the deposit's history, and it provides a framework to guide exploration for similar deposits elsewhere. The second study of this dissertation tested whether fluorite records the REE composition of its source. Fluorite was synthesized from REE-bearing solutions from 25–150 °C. Fluorite REE patterns are consistent with the parent solution under all tested conditions. Application to the Baiyanghe deposit indicates that while the REE pattern of some fluorite matches the source, many reflect changes in fluid composition or post-crystallization alteration. Fluorite REE patterns therefore may reflect the source but also track fluid evolution. The third study investigated the Gallinas Mountains REE deposits, New Mexico, where the source of the REEs is debated. New Nd–Sr (εNdCHUR(T) = −3.7 to −2.1; 87Sr/86Sri = 0.70642–0.70878) and barite O–S isotope ratios (δ18OVSMOW = 0.0 to +5.6‰; δ34SCDT = +8.2 to +11.8‰) indicates the mineralizing fluids are sourced from the subvolcanic rocks and interacted with the country rocks. The fluids concentrated REE ores at depth, and surface waters later remobilized copper into the overlying sandstone. This new model suggests exposed secondary copper minerals may indicate underlying economic REE ore. Together, these studies clarify how critical metal deposits form, link surface clues to deeper resources, and provide new tools for understanding and exploring for the metals needed in advanced technologies and the clean energy transition.

Author dc:creator

• Jacques, Issac

Advisor dc:contributor.supervisor

• Fayek, Mostafa

• Critical metals
• Be
• REEs
• Magmatic-Hydrothermal

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1993/39686

OAI record oai:identifier

https://mspace.lib.umanitoba.ca/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Amspace.lib.umanitoba.ca%3A1993%2F39686